EP2615307A1 - Screw rotor for a screw vacuum pump - Google Patents
Screw rotor for a screw vacuum pump Download PDFInfo
- Publication number
- EP2615307A1 EP2615307A1 EP12000151.6A EP12000151A EP2615307A1 EP 2615307 A1 EP2615307 A1 EP 2615307A1 EP 12000151 A EP12000151 A EP 12000151A EP 2615307 A1 EP2615307 A1 EP 2615307A1
- Authority
- EP
- European Patent Office
- Prior art keywords
- rotor
- screw
- shaft
- rotors
- core
- 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.)
- Granted
Links
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Images
Classifications
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- 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
-
- 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
- F04C2/00—Rotary-piston machines or pumps
- F04C2/08—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing
- F04C2/12—Rotary-piston machines or pumps of intermeshing-engagement type, i.e. with engagement of co-operating members similar to that of toothed gearing of other than internal-axis type
- F04C2/14—Rotary-piston machines or pumps 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
- F04C2/16—Rotary-piston machines or pumps 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
- F04C18/12—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
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/0042—Driving elements, brakes, couplings, transmissions specially adapted for pumps
- F04C29/0078—Fixing rotors on shafts, e.g. by clamping together hub and shaft
-
- 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
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/0042—Driving elements, brakes, couplings, transmissions specially adapted for pumps
- F04C29/0085—Prime movers
-
- 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
- F04C29/00—Component parts, details or accessories of pumps or pumping installations, not provided for in groups F04C18/00 - F04C28/00
- F04C29/04—Heating; Cooling; Heat insulation
Definitions
- the invention relates to a screw rotor for a screw vacuum pump having the features of the preamble of claim 1 and a screw vacuum pump with corresponding screw rotors having the features of the preamble of claim 13,
- membrane vacuum pumps are advantageous because the pumping chamber is hermetically separated from the drive region by the gas-tight clamped membrane. Due to the limited compression ratio and the mostly operated only by the gas flow valves, however, pressures below 50 Pa can be achieved only with difficulty.
- screw vacuum pumps short: screw pumps
- two helical rotors are non-contact in a suitably shaped screw pump stator with each other, so that by their opposite rotation gas is conveyed from an inlet to an outlet.
- All versions here as in the following refer to non-contact, oil-free screw pumps.
- Screw pumps An advantage of the screw pumps is the high possible compression, as screw pumps can be built intrinsically multi-stage, each screw acts as a stage. Screw pumps thus offer the possibility of achieving a good ultimate vacuum in the range of ⁇ 1 Pa with only one pair of rotors.
- a general problem with screw pumps is the high heat release, especially in the area of the atmosphere-side compression. At low suction pressures, only a small amount of gas is conveyed from the suction side to the atmosphere side. So there is only a small gas exchange within the pump. In addition, until the last atmosphere-side screw thread in the pump chambers, which are formed by the meshing screw flights, a negative pressure,
- the backflow of the gas can be reduced by closely fitting end plates with openings at suitable positions on the screw rotor. However, since these end plates hinder the gas discharge at the same time, this arrangement can hardly be improved.
- check valves on such end plates. However, these would have to open and close with the rotational frequency of the rotors, but the frequency of type, 6000 - 25000 However, min -1 is usually too high, ie check valves of sufficient size are too slow to react.
- screw rotors are commonly used with decreasing to the outlet pump chamber volume. This can be achieved for example by reduced helical pitch or reduced helical radius to the outlet side. This results in an internal compression of typically 2-10. In this way, the power requirement of the pump as well as the heat release at the atmosphere end of the screw relative to the pump's pumping speed can be reduced by almost this compression factor.
- a disadvantage of this method is that the production of the rotors is significantly more difficult due to the constant or even erratic screw profile change.
- Another disadvantage is that the internal compression at high suction pressures can lead to internal overpressures. This can overload the drive motor and cause damage to the pump. Often therefore complicated pressure relief valves in the pump chamber stator in the field of internal compression are required. When pumping incompressible fluids - be they aspirated or caused by condensation inside - can result in hydrostatic blocking, with the result that the pump stops suddenly due to the overload. This can result in expensive consequential damage to the unit and drive.
- liquid cooling of the pump housing is frequently used in known larger screw pumps.
- liquid internal cooling of the rotors are used, but they are expensive.
- a disadvantage of conventional steels and cast iron alloys is the limited chemical resistance. Aggressive chemicals have to be removed from such pumps with cold traps or similar. be kept away. In addition, it is often worked with purge gas, which is expensive. Nevertheless, such pumps often show only short service lives when pumping aggressive media.
- Hastelloy Chemically highly resistant steel alloys such as Hastelloy are usually difficult to machine, which makes the production of the often complicated shaped and tightly tolerated screw profiles consuming and expensive.
- rotors made of chemically resistant plastics would be advantageous. Due to the limited stiffness (low modulus of elasticity) of plastics, a shaft of stiffer material is generally required inside the rotor. Such an arrangement, consisting of a rotor made of plastic with a steel rotor shaft inside, is known ( WO 2010/061939 A1 ).
- a disadvantage of the aforementioned arrangement is that almost all practically usable plastics have a low thermal conductivity, even with a high filler content such as carbon fiber can hardly be a heat conduction greater than 1 W / m. K achieve.
- the high thermal expansion is disadvantageous because then the fast (typ.> 6000 min -1 ) with a close distance (typ. ⁇ 0.1 mm) can touch each other running rotors, which can lead to significant consequential damage.
- the starting point of the invention is the realization that the cooling of the screw rotor must be carried out with compact screw pumps mainly by heat dissipation through the rotor and the rotor shaft from the pump chamber out, according to the invention is provided to the rotor with a Build rotor core of a highly heat conductive material, which is surrounded by a rotor shell, preferably made of a chemically resistant plastic.
- Highly thermally conductive material used are materials having a thermal conductivity of more than 100 W / m.K, preferably more than 200 W / m.K, for example aluminum or copper and some alloys. Plastics and iron alloys (steel, cast iron) do not reach these values and do not have sufficient heat dissipation for effective cooling of the rotor inwards or over the rotor shaft.
- the rotor shaft is made of a highly heat-conductive material, so that the heat from the rotor via the rotor shaft by solid-state heat conduction is transported out of the pump chamber. It is particularly useful in this case if the rotor shaft with the rotor core is made in one piece, since then the solid state heat conduction takes place inside the rotor core without disturbing interfaces up to the rotor shaft to the outside,
- a hollow shaft is used for the rotor shaft instead of a solid, highly heat-conductive material, through which a cooling gas such as e.g. Air is conveyed, which is preferably sucked by the rotation of the shaft itself, for example by a kind of blower on a free shaft end.
- the cooling gas is conducted through the rotor shafts into the area of the highest heat release and cools the highly heat-conductive rotor core from the inside.
- the heated gas is discharged, for example, into the outlet of the pump, where it can serve as purge gas, or guided back through the rotor shaft.
- the rotor thus consists of a highly thermally conductive rotor core, which is surrounded by a rotor shell, wherein the rotor core is in contact with the hollow rotor shaft or directly with the cooling gas.
- the material of the hollow rotor shaft can also be highly heat-conductive.
- the thickness of the cladding material results on the one hand from the need for the layer to be diffusion-tight and mechanically stable and, on the other hand, from the fact that the heat conduction through the layer to the core material is still sufficiently high to overheat the surface avoid.
- the highly heat-conductive material has at least in this section Screw profile (reduced by the sheath wall thickness), wherein the sheath material in these areas preferably has a thickness of 0.1 - 10 mm.
- the rotor shell often has only a comparatively low specific thermal conductivity of mostly ⁇ 5 W / m ⁇ K (typically for plastics, for example), due to the small thickness of the rotor shell sufficient heat dissipation is achieved by this layer to the rotor core.
- the highly thermally conductive rotor core preferably in the region of the highest heat release, ie at the atmosphere-side end of the rotor, in which a high heat dissipation through the rotor is required, extends outward into the screw threads.
- the rotor according to the invention has one or more sections in which the highly heat-conductive rotor core does not extend or not completely outwards into the screw threads.
- possible materials for the rotor core and the rotor shell are considered.
- the wrapping of a rotor core can be done in several ways. If a very thin coating ( ⁇ 0.1 mm) is applied, it may be possible to dispense with mechanical reworking of the layer. Often, however, such layers are not completely diffusion-tight, so that the layer can be infiltrated by the pumped media and then peeled off under vacuum. For thicker coatings, the screw profile form must be reworked consuming. Thicker coatings are usually melted after application (e.g., by electrostatic powder coating). This often leads to the rounding of the edges, resulting in defects after finishing on outer edges.
- the encapsulation of a rotor core with a thermoplastic material is the encapsulation of a rotor core with a thermoplastic material.
- the layer thickness can be almost arbitrary (ie, diffusion-tight) choose and the edges are accurately formed.
- this method allows to fill even larger volumes of plastic.
- the second aspect of the invention that is, that the highly thermally conductive core material only where thermally necessary, ie in particular in the area of the atrilosphDCen departmenten compression, outwardly to close under the plastic surface, particularly advantageous.
- less thermally stressed areas of the rotor can be dispensed with the formation of the core material into the screw threads into it and the rotor can there consist of a relatively small cylindrical rotor core surrounded by plastic as a rotor shell.
- As sheathing material preferably chemically highly resistant plastics such as PPS, PEEK or fluoroplastics are used, which are preferably reinforced with fillers such as carbon or glass fiber.
- PEEK with carbon fiber reinforcement only about 16% of the density of copper.
- the arrangement according to the invention thus provides a rotor with chemically highly resistant and diffusion-tight surface at the same time very high heat conduction of the overall arrangement - at least in the field of large heat release during operation - at surprisingly low production costs.
- the latter arises because materials such as copper or aluminum are used only where necessary, material-saving manufacturing processes such as injection molding are used, and the materials are easily editable.
- a form-fit connection is necessary, if possible, with undercuts to the toothing, if sufficient material adhesion can not be achieved.
- grooves, bores or grooves can be introduced into the rotor core. Even a rough surface of the rotor core, for example, by sandblasting is helpful.
- the advantages of the rotor according to the invention are particularly clear in the preferred arrangement of the screw pump with overhung rotors.
- the storage and drive area is preferably under ambient air pressure and not in contact with the pumped media. So that this storage and drive area not with a shaft seal o.ä. must be sealed to the suction chamber, the pressure side of the pump unit is usually arranged on the drive side.
- This area is thermally loaded twice, on the one hand by the engine, on the other hand by the heat of compression at the atmosphere-side screw rotor end.
- the drive range is quite simply durable to a low operating temperature.
- the waste heat from the compression can be a multiple of the engine waste heat.
- the rotor assembly according to the invention now allows a very effective dissipation of the heat of compression from the pump chamber in the direction of the well-cooled drive range using the highly heat-conductive rotor shaft of a solid material.
- a means for delivering this heat to the surrounding air is located in the drive region on the rotor shaft.
- This may be, for example, a revolving fan or discs, for example, copper or aluminum. These very effectively release the heat from the rotor shaft to the air due to the rapid rotation.
- the heated air can be removed by an externally applied cooling air flow.
- a generated by a follower fan air flow can also be used to cool the engine.
- the second aspect of the invention is particularly important according to which the highly thermally conductive rotor core (often with high density) outside the thermally highly stressed part of the rotor is not pulled close to the plastic surface, but rather is reduced as far as possible. This significantly reduces the moving masses, especially at the end of the rotor remote from the bearing.
- a reception of the rotor in the processing machine is also required on the side facing away from the bearing for dimensionally stable machining of the rotors (in the pump). If the rotor shell is unsuitable for this, the highly thermally conductive rotor core can also be guided on the side facing away from the bearing to the outside. If necessary, this area must be protected later from corrosion attack, for example, by covering with a plug, for example made of PTFE. Alternatively, the frontal recording with Help a high corrosion resistant metal such as Hastelloy, which is firmly connected to the core material done.
- the highly thermally conductive rotor core and / or the rotor shaft is not present over the entire length of the screw rotor with a full cross-section, or hollow, or completely absent.
- the part of the rotor facing away from the storage can then consist of solid wrapping material or have a recess. All these characteristics lead to a significant reduction of the moving masses in the bearing remote area of the rotor.
- the production of the highly heat-conductive rotor core for example, made of copper or aluminum or an alloy can be made from solid, or preferably by attaching a hollow screw on a shaft or by connecting a solid screw with a short shaft. Both reduce the cost of materials for the production.
- the rotor core as a whole or the hollow screw is precast or the latter consists of a correspondingly bent sheet metal part.
- further functional elements of the rotor are integrated into the rotor shell. This can be, for example, balancing weights on one or both sides of the screw, or also Spülgaslproper, as in DE 10 2010 055 798 A1 disclosed,
- the drive of the screw pump is effected by a two-shaft synchronous drive, consisting of magnetized cylinders on each of the two rotor shafts, which synchronize the rotors in opposite directions by their mutual magnetic interaction.
- the two magnetized cylinders are surrounded by one or more windings, which generate suitable magnetic field by moving current, so that the two magnetized cylinders and thus the rotor shafts rotate synchronously in opposite directions.
- Fig. 1 shows a screw rotor 1 according to the invention in section.
- the rotor 1 is intended for use in a screw vacuum pump, preferably in one with a pumping speed of less than 50 m 3 / h.
- rotor 1 consists in principle of a rotor shaft 2, a seated on the rotor shaft 2 rotor core 3 and a seated on the rotor core 3 rotor shell 4. Shown is the rotor shaft 2 separately from the rotor core 3. Basically, it is also possible that the rotor shaft 2 and the rotor core 3 are formed integrally with each other.
- the rotor shell 4 surrounds the rotor core 3 at least partially.
- the rotor shell 4 surrounds the rotor core 3 on the rotor shaft 2 on all outer surfaces, ie on all surfaces that do not abut the rotor shaft 2.
- the rotor core 3 is made of a material having a high thermal conductivity of more than 100 W / m ⁇ K, preferably a thermal conductivity of more than 200 W / m ⁇ K.
- the rotor shaft 2 is preferably made of a material , which has a high thermal conductivity, preferably also here a thermal conductivity of more than 100 W / m ⁇ K.
- the rotor shaft 2 may have one or more channels running parallel to its axis for supplying gas in the direction of the rotor core 3, so that the rotor 1 is cooled overall from the inside.
- the rotor core 3 in individual sections of the rotor 1 can reach into its screw threads as in FIG Fig. 1 is shown in area 5.
- the rotor core 3 has almost the outer dimensions of the rotor 1 in total, with only a thin, the rotor shell 4 forming layer. In this range, one can for the rotor shell 4 thicknesses between 0.1 mm and 10 mm in the eye.
- This construction will be realized in particular where significant heat development occurs during operation of the rotor 1 in a screw vacuum pump, ie in particular where the compression takes place to atmospheric pressure, close to the outlet of a pump chamber of a screw vacuum pump.
- this invention is preferably made of a material which has a low thermal conductivity in comparison with the thermal conductivity of the rotor core 3 and the rotor shaft 2, preferably a thermal conductivity of less than 5 W / m ⁇ K.
- the rotor shell 4 made of plastic in particular consists of a thermoplastic material.
- the plastic chemically resistant for example PPS, PEEK or fluoroplastic.
- the strength of the plastic of the rotor shell 4 can be increased by fillers such as glass fibers or carbon fibers.
- the rotor shell 4 is connected in an injection molding process with the rotor core 3, that has been applied to this.
- the materials recommended are copper or aluminum or alloys of these materials.
- Fig. 1 shows the rotor shaft 2 of the rotor 1 projecting at both ends, that is, substantially axially projecting relative to the rotor core 3 and the rotor shell 4. This is a rotor 1 mounted at both ends.
- the rotors 1, 1 ' which in the screw vacuum pump of Fig. 2 are shown built for a one-sided storage at one end.
- the rotor shaft 2 protrudes axially only at its end serving for storage relative to the rotor core 3 and the rotor shell 4 axially, namely into a storage area.
- the rotor shaft 2 and / or the rotor core 3 in the region of the end of the rotor 1, 1 'facing away from the bearing end, depending on the distance from the storage serving end has a reduced cross-section, has a recess or is completely absent, with respect to the full outer dimensions of the rotor 1, 1 'missing volume is filled by the rotor shell 4.
- Fig. 2 shows a schematic sectional view of a screw vacuum pump with inserted therein, inventively designed, standing in mutual non-contact engagement helical rotors 1, 1 '.
- the screw vacuum pump off Fig. 2 initially has a screw pump stator 8, which practically forms the housing of the screw vacuum pump.
- the screw pump stator 8 is a to the rotors 1, 1 'suitably shaped pumping chamber 9 with at least one inlet 10 and an outlet 11.
- the gaseous medium from Inlet 10 promoted to the outlet 11.
- the rotors 1, 1 ' are configured with rotor shaft 2, rotor core 3 and rotor shell 4, as described above in connection with FIG Fig. 1 illustrated rotor 1 has been explained in detail.
- the rotors 1, 1 'in the embodiment of Fig. 2 differ from the rotor 1 in Fig. 1 in that the rotors 1, 1 'are here in a flying manner, that is, they are mounted only on one side. At the opposite end of the rotors 1, 1 ', ie in Fig. 2 above, there are no bearings.
- Fig. 2 is located below the pump chamber 9 in synchronenpumpenstator 8 a storage and drive range in which the rotor shafts 2 of the rotors 1, 1 'are mounted. It can be seen that the outlet 11 of the pumping chamber 9 is arranged at the end of the pumping chamber 9 facing the mounted ends of the rotors 1, 1 '.
- the storage and drive range is preferably under ambient air pressure. It contains means for storage 12, 12 '; 13, 13 'of the rotors 1, 1', as well as means for synchronization and / or for driving the rotors 1, 1 ', in the example shown here, the latter consist of suitably magnetized cylinders 14, 14', the rotors by their mutual magnetic interaction 1, 1 'synchronize in opposite directions.
- the two magnetized cylinders 14, 14 ' are surrounded by one or more windings 15, 15' which generate magnetic fields traveling through suitable energization, so that the two magnetized cylinders 14, 14 'and thus the rotor shafts 2 of the rotors 1, 1' rotate synchronously in opposite directions.
- the drive of the screw vacuum pump is thus here as a two-shaft synchronous drive 14, 14 '; 15, 15 'executed.
- Such constructions are known per se from the prior art.
- heat emission means 16, 16 'for emitting heat which has been conducted here via the rotor shafts 2, to the surrounding air are shown on the shaft.
- This may be, for example, revolving fan wheels or discs, the heated air can be removed by a cooling air flow applied from the outside (not shown).
- Fig. 2 further functional elements 17, 17 'indicated, which can serve for example the balancing. Or it is purge gas to aspirate purge gas from the storage area and thus to flush the bearings.
- the rotor shell 4 of the respective rotor 1, 1 ' has axially extending recesses. Below the recesses, the rotor shell 4 of both rotors 1,1 'each extend transversely to the axis of the rotor 1, 1' over the complete cross section of the rotor 1, 1 ', because the respective rotor shaft 2 already ends shortly below this range.
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Abstract
Description
Die Erfindung betrifft einen Schraubenrotor für eine Schraubenvakuumpumpe mit den Merkmalen des Oberbegriffs von Anspruch 1 sowie eine Schraubenvakuumpumpe mit entsprechenden Schraubenrotoren mit den Merkmalen des Oberbegriffs von Anspruch 13,The invention relates to a screw rotor for a screw vacuum pump having the features of the preamble of
Zahlreiche Prozesse in Forschung und Industrie erfordern ein Vakuum im Bereich 102 Pa bis 10-2 Pa (Feinvakuumbereich), wobei häufig auch kondensierende und/oder aggressive Dämpfe oder Gase gefördert werden müssen. Zur Erzeugung eines Unterdrucks in diesem Bereich werden oft flüssigkeitsgedichtete oder -geschmierte Vakuumpumpen wie beispielsweise ölgedichtete Drehschieberpumpen eingesetzt. Die Verwendung von solchen Pumpen, bei denen das gepumpte Medium mit Öl oder anderen Flüssigkeiten in Berührung kommt, hat zahlreiche Nachteile. So können die gepumpten Medien den Schmierstoff verunreinigen oder mit ihm reagieren, was die Schmier- und Dichtwirkung herabsetzt. Rückströmung von gasförmigen Komponenten oder Zersetzungsprodukten des Schmierstoffes in die Prozessanlage kann die dortigen Prozesse empfmdlich stören.Numerous processes in research and industry require a vacuum in the range of 10 2 Pa to 10 -2 Pa (fine vacuum range), which often also condensing and / or aggressive vapors or gases must be promoted. To generate a negative pressure in this area, liquid-sealed or lubricated vacuum pumps such as oil-sealed rotary vane pumps are often used. The use of such pumps, in which the pumped medium comes into contact with oil or other liquids, has numerous disadvantages. Thus, the pumped media can contaminate or react with the lubricant, which reduces the lubricity and sealing effect. Backflow of gaseous components or decomposition products of the lubricant into the process plant can sensitively disturb the processes there.
Aus diesem Grund wird seit langem an der Entwicklung sogenannter "trockener" Vakuumpumpen gearbeitet, also von Pumpen, bei denen die gepumpten Medien nicht mit einer Flüssigkeit in Berührung kommen.For this reason, the development of so-called "dry" vacuum pumps, ie pumps in which the pumped media does not come into contact with a liquid, has long been the subject of much work.
Bei höheren Drücken, d.h. im Bereich 105 Pa bis 102 Pa, sind Membranvakuumpumpen vorteilhaft, da der Schöpfraum durch die gasdicht eingespannte Membran hermetisch vom Antriebsbereich abgetrennt ist. Durch das begrenzte Verdichtungsverhältnis und die meist nur durch die Gasströmung betätigten Ventile lassen sich jedoch Drücke unterhalb 50 Pa nur schwer erreichen.At higher pressures, ie in the
Neben Feinvakuumpumpen wie Kolbenpumpen, Scrollpumpen, Klauenpumpen und Rootspumpen sind auch Schraubenvakuumpumpen bekannt.In addition to fine vacuum pumps such as piston pumps, scroll pumps, claw pumps and Roots pumps also screw vacuum pumps are known.
Bei Schraubenvakuumpumpen (kurz: Schraubenpumpen) kämmen zwei schraubenförmige Rotoren berührungslos in einem geeignet geformten Schraubenpumpenstator miteinander, so dass durch ihre gegenläufige Drehung Gas von einem Einlass zu einem Auslass gefördert wird. Alle Ausführungen hier wie im folgenden beziehen sich auf berührungslos verdichtende, ölfreie Schraubenpumpen.In screw vacuum pumps (short: screw pumps), two helical rotors are non-contact in a suitably shaped screw pump stator with each other, so that by their opposite rotation gas is conveyed from an inlet to an outlet. All versions here As in the following refer to non-contact, oil-free screw pumps.
Ein Vorteil der Schraubenpumpen ist die hohe mögliche Verdichtung, da Schraubenpumpen intrinsisch vielstufig aufgebaut werden können, wobei jeder Schraubengang als Stufe wirkt. Damit bieten Schraubenpumpen die Möglichkeit, mit nur einem Rotorpaar ein gutes Endvakuum im Bereich < 1 Pa zu erzielen.An advantage of the screw pumps is the high possible compression, as screw pumps can be built intrinsically multi-stage, each screw acts as a stage. Screw pumps thus offer the possibility of achieving a good ultimate vacuum in the range of <1 Pa with only one pair of rotors.
Bei Schraubenpumpen ist eine sogenannte fliegende Lagerung dieses Rotorpaars möglich. Bei einer fliegenden Lagerung erfolgt die Lagerung nur von einer Seite des Rotorpaars aus. Auf der anderen Seite des Rotorpaars ist keine Lagerung vorhanden. Damit kann der Schraubenpumpenstator ohne Lagerungseinheit ausgeführt werden. Das erlaubt eine einfache Demontage des Schraubenpumpenstators z.B. für Wartungs- und Reinigungszwecke.With screw pumps a so-called flying bearing of this pair of rotors is possible. In a flying storage, storage takes place only from one side of the rotor pair. There is no storage on the other side of the rotor pair. Thus, the screw pump stator can be performed without a storage unit. This allows easy disassembly of the screw pump stator, e.g. for maintenance and cleaning purposes.
Ein generelles Problem bei Schraubenpumpen ist die hohe Wärmefreisetzung gerade im Bereich der atmosphärenseitigen Verdichtung, Bei niedrigen Ansaugdrücken wird von der Saugseite nur wenig Gas zur Atmosphärenseite gefördert. Es erfolgt also nur geringer Gasaustausch innerhalb der Pumpe. Darüber hinaus herrscht bis zum letzten atmosphärenseitigen Schraubengang in den Schöpfräumen, die von den kämmenden Schraubengängen gebildet werden, ein Unterdruck,A general problem with screw pumps is the high heat release, especially in the area of the atmosphere-side compression. At low suction pressures, only a small amount of gas is conveyed from the suction side to the atmosphere side. So there is only a small gas exchange within the pump. In addition, until the last atmosphere-side screw thread in the pump chambers, which are formed by the meshing screw flights, a negative pressure,
Beim Öffnen des Schöpfraums am letzten atmosphärenseitigen Schraubengang im Zuge der Drehung des Rotors strömt Gas aus dem Auslass zurück in diesen Schöpfraum. Das eingeströmte Gas wird zusammen mit dem vom Saugstutzen hierher geförderten Gas im Zuge der Drehung der Rotoren wieder herausgedrückt. Dieses Pulsieren des Gases am Auslass verursacht einen hohen Antriebsleistungsbedarf und setzt große Wärmemengen in einem relativ kleinen Volumen frei.When opening the pump chamber at the last atmosphere-side screw thread in the course of the rotation of the rotor gas flows from the outlet back into this pump chamber. The gas that has flowed in is pushed out again together with the gas conveyed from the suction connection in the course of the rotation of the rotors. This pulsation of the gas at the outlet causes a high drive power requirement and releases large amounts of heat in a relatively small volume.
Das Rückströmen des Gases kann durch am Schraubenrotor eng anliegende Endplatten mit Öffnungen an geeigneten Positionen verringert werden. Da diese Endplatten den Gasausstoß jedoch gleichzeitig behindern, ist durch diese Anordnung kaum eine Verbesserung zu erzielen.The backflow of the gas can be reduced by closely fitting end plates with openings at suitable positions on the screw rotor. However, since these end plates hinder the gas discharge at the same time, this arrangement can hardly be improved.
Ein anderer Ansatz zur Verringerung der Rückströmung sind Rückschlagventile an solchen Endplatten. Diese müßten jedoch mit der Umdrehungsfrequenz der Rotoren öffnen und schließen, Dafür ist die Frequenz von typ, 6000 - 25000 min-1 jedoch meist zu hoch, d.h. Rückschlagventile von ausreichender Größe reagieren zu träge.Another approach to reducing backflow are check valves on such end plates. However, these would have to open and close with the rotational frequency of the rotors, but the frequency of type, 6000 - 25000 However, min -1 is usually too high, ie check valves of sufficient size are too slow to react.
Um das Temperatur- und Leistungs-Problem zu verringern, werden verbreitet Schraubenrotoren mit zum Auslass hin abnehmendem Schöpfraumvolumen eingesetzt. Dies kann beispielsweise durch verringerte Schraubensteigung oder verringerten Schraubenradius zur Auslassseite hin erreicht werden. Dies bewirkt eine interne Verdichtung von typisch 2 - 10. Auf diese Weise kann der Leistungsbedarf der Pumpe sowie die Wärmefreisetzung am atmosphärenseitigen Ende der Schraube bezogen auf das Saugvermögen der Pumpe nahezu um diesen Verdichtungsfaktor reduziert werden.In order to reduce the temperature and power problem, screw rotors are commonly used with decreasing to the outlet pump chamber volume. This can be achieved for example by reduced helical pitch or reduced helical radius to the outlet side. This results in an internal compression of typically 2-10. In this way, the power requirement of the pump as well as the heat release at the atmosphere end of the screw relative to the pump's pumping speed can be reduced by almost this compression factor.
Nachteilig an dieser Methode ist, dass die Herstellung der Rotoren durch die stetige oder auch sprunghafte Schraubenprofiländerung deutlich schwieriger wird. Ein weiterer Nachteil ist, dass die interne Verdichtung bei hohen Ansaugdrücken zu inneren Überdrücken führen kann. Dies kann den Antriebsmotor überlasten und Schäden an der Pumpe hervorrufen. Oft sind daher aufwendige Überdruckventile im Schöpfraumstator im Bereich der internen Verdichtung erforderlich. Bei Förderung von inkompressiblen Flüssigkeiten - seien sie angesaugt oder aufgrund von Kondensation im Inneren entstanden - können sich hydrostatische Verblockungen ergeben, mit der Folge, dass die Pumpe aufgrund der Überlastung schlagartig stehen bleibt. Dies kann teure Folgeschäden am Aggregat und Antrieb zur Folge haben.A disadvantage of this method is that the production of the rotors is significantly more difficult due to the constant or even erratic screw profile change. Another disadvantage is that the internal compression at high suction pressures can lead to internal overpressures. This can overload the drive motor and cause damage to the pump. Often therefore complicated pressure relief valves in the pump chamber stator in the field of internal compression are required. When pumping incompressible fluids - be they aspirated or caused by condensation inside - can result in hydrostatic blocking, with the result that the pump stops suddenly due to the overload. This can result in expensive consequential damage to the unit and drive.
Ein anderer Lösungsansatz ist, zwei getrennte Schraubenpumpen mit unterschiedlichem Saugvermögen in Serienschaltung zu verwenden, die jede für sich keine interne Verdichtung aufweisen (siehe
Um die Thermik zu beherrschen wird bei bekannten größeren Schraubenpumpen häufig eine Flüssigkeitskühlung des Pumpengehäuses verwendet. Bei größeren Pumpen kommen auch Flüssigkeits-Innenkühlungen der Rotoren zur Anwendung, die jedoch aufwendig sind.In order to control the thermals, liquid cooling of the pump housing is frequently used in known larger screw pumps. For larger pumps and liquid internal cooling of the rotors are used, but they are expensive.
Nicht selten wird auch in den Bereich der letzten atmosphärenseitigen Schraubengänge Gas von außen in den Schöpfraum eingelassen. Das Spülgas kühlt diesen Bereich und transportiert erhitztes Gas weg von den letzten Schraubengängen. Nachteilig ist der hohe Aufwand sowie die unvermeidliche Verschlechterung des Endvakuums der Pumpe.It is not uncommon for gas to be admitted from the outside into the pump chamber even in the region of the last atmosphere-side screw flights. The purge gas cools this area and transports heated gas away from the last Convolutions. A disadvantage is the high cost and the inevitable deterioration of the final vacuum of the pump.
Für kompakte Schraubenpumpen mit typischen Rotorabständen von 20 - 100 mm und Saugvermögen < 50m3/h läßt sich aus Platz- und Kostengründen keine Flüssigkeits-Innenkühlung der Rotoren anwenden. Auch eine Flüssigkeitskühlung des Gehäuses wäre bei solchen Geräten nachteilig, da diese flexibel z.B. in Forschungslaboratorien eingesetzt werden sollen, während die üblichen, deutlich größeren Pumpen schon aus Gewichtsgründen meist ortsfest in industriellen Anlagen installiert werden. Kompakte Schraubenvakuumpumpen erfordern also neuartige Wege, die schwierige thermische Situation am atmosphärenseitigen Ende der Rotoren zu beherrschen.For compact screw pumps with typical rotor spacings of 20-100 mm and pumping speed <50 m 3 / h, it is not possible to use liquid internal cooling of the rotors for space and cost reasons. A liquid cooling of the housing would be disadvantageous in such devices, since they are to be used flexibly, for example, in research laboratories, while the usual, much larger pumps are mostly already installed for weight reasons stationary in industrial plants. Compact screw vacuum pumps thus require novel ways of coping with the difficult thermal situation at the atmosphere-side end of the rotors.
Ein weiterer Aspekt für kompakte Schraubenvakuumpumpen ist die Materialauswahl für die Rotoren. Üblicherweise bestehen solche Schraubenrotoren, die oft einteilig mit den Rotorwellen ausgeführt werden, aus Gußeisen- oder Stahllegierungen, da diese eine hohe Steifigkeit (E-Modul) und gute Bearbeitbarkeit aufweisen. Die Wärmeleitfähigkeit dieser Materialklasse ist nur mittelmäßig, reicht in Verbindung mit äußerer Wasserkühlung und ggf. innerer Ölkühlung i,A. aber aus. Auch sind bei solchen Materialien Temperaturen der Rotoren von > 150°C an der Oberfläche noch akzeptabel.Another aspect for compact screw vacuum pumps is the selection of materials for the rotors. Usually, such screw rotors, which are often made integral with the rotor shafts, are made of cast iron or steel alloys because they have high rigidity (Young's modulus) and good workability. The thermal conductivity of this material class is only mediocre, sufficient in conjunction with external water cooling and possibly internal oil cooling i, A. but out. Even with such materials temperatures of the rotors of> 150 ° C at the surface are still acceptable.
Nachteilig an herkömmlichen Stählen und auch Gußeisenlegierungen ist die nur begrenzte chemische Beständigkeit. Aggressive Chemikalien müssen von solchen Pumpen mit Kühlfallen o.ä. ferngehalten werden. Zudem wird häufig mit Spülgas gearbeitet, was aufwendig ist. Dennoch zeigen solche Pumpen beim Fördern aggressiver Medien oft nur kurze Standzeiten.A disadvantage of conventional steels and cast iron alloys is the limited chemical resistance. Aggressive chemicals have to be removed from such pumps with cold traps or similar. be kept away. In addition, it is often worked with purge gas, which is expensive. Nevertheless, such pumps often show only short service lives when pumping aggressive media.
Chemisch hochbeständige Stahllegierungen wie Hastelloy lassen sich meist nur schwierig bearbeiten, was die Fertigung der oft kompliziert geformten und eng tolerierten Schraubenprofile aufwendig und teuer macht.Chemically highly resistant steel alloys such as Hastelloy are usually difficult to machine, which makes the production of the often complicated shaped and tightly tolerated screw profiles consuming and expensive.
Ein weiterer Nachteil von Stahl- oder Gußrotoren ist das hohe Gewicht, das sich negativ auf die benötigte Antriebsleistung beim Beschleunigen sowie die Unwucht der Rotoren auswirkt. Ansätze für die Vermeidung dieses Problems mit Hilfe eines Rotors aus Aluminium auf einer Stahlwelle sind bekannt (
Für Anwendungen mit chemisch aggressiven Stoffen wären Rotoren aus chemisch beständigen Kunststoffen vorteilhaft. Aufgrund der nur begrenzten Steifigkeit (niedriges E-Modul) von Kunststoffen ist im Allgemeinen eine Welle aus steiferem Material im Inneren des Rotors erforderlich. Eine solche Anordnung, bestehend aus einem Rotor aus Kunststoff mit einer Stahl-Rotorwelle im Inneren, ist bekannt (
Nachteilig an der zuvor genannten Anordnung ist, dass nahezu alle praktisch verwendbaren Kunststoffe eine geringe Wärmeleitfähigkeit aufweisen, Selbst mit hohem Füllstoffanteil wie z.B. Kohlefaser läßt sich kaum eine Wärmeleitung größer als 1 W/m . K erzielen. Für die Anwendung in der Schraubenpumpe bedeutet dies, dass bei hoher Wärmefreisetzung am atmosphärenseitigen Ende des Rotors die Wärme nicht ausreichend abtransportiert wird und sich das Kunststoffmaterial dort lokal schnell auf hohe Temperaturen erhitzt. Dies kann zu hoher thermischer Ausdehnung oder sogar thermischer Schädigung (Zersetzung, Schmelzen) des Materials führen. Die hohe thermische Ausdehnung ist nachteilig, da sich dann die schnell (typ. > 6000 min-1) mit engem Abstand (typ. < 0,1 mm) aneinander vorbei laufenden Rotoren berühren können, was zu erheblichen Folgeschäden führen kann.A disadvantage of the aforementioned arrangement is that almost all practically usable plastics have a low thermal conductivity, even with a high filler content such as carbon fiber can hardly be a heat conduction greater than 1 W / m. K achieve. For use in the screw pump, this means that with high heat release at the atmosphere-side end of the rotor, the heat is not sufficiently removed and the plastic material there locally heated quickly to high temperatures. This can lead to high thermal expansion or even thermal damage (decomposition, melting) of the material. The high thermal expansion is disadvantageous because then the fast (typ.> 6000 min -1 ) with a close distance (typ. <0.1 mm) can touch each other running rotors, which can lead to significant consequential damage.
Die zuvor geschilderten Probleme bei Schraubenrotoren für eine Schraubenvakuumpumpe sind im Stand der Technik bereits angesprochen worden (
Ausgehend von dem zuletzt erläuterten Stand der Technik liegt der Lehre das Problem zugrunde, einen Schraubenrotor für eine Schraubenvakuumpumpe anzugeben, bei dem ein Einsatz im Labor unter chemisch aggressiven Bedingungen jedenfalls konstruktiv möglich ist und gleichwohl die zuvor geschilderten thermischen Probleme gelöst sind.Starting from the last-mentioned prior art, the teaching is based on the problem to provide a screw rotor for a screw vacuum pump, in which a use in the laboratory under chemically aggressive Conditions in any case constructively possible and nevertheless the previously described thermal problems are solved.
Das zuvor aufgezeigte Problem ist bei einem Schraubenrotor für eine Schraubenvakuumpumpe mit den Merkmalen des Oberbegriffs von Anspruch 1 durch die Merkmale des kennzeichnenden Teils von Anspruch 1 gelöst.The above-mentioned problem is solved in a screw rotor for a screw vacuum pump having the features of the preamble of
Bevorzugte Ausgestaltungen und Weiterbildungen des erfindungsgemäßen Rotors sind Gegenstand der Ansprüche 2 bis 12.Preferred embodiments and further developments of the rotor according to the invention are the subject matter of
Bezogen auf eine Schraubenvakuumpumpe insgesamt, die zwei in gegenseitigem berührungslosem Eingriff miteinander stehende schraubenförmige Rotoren in einem passend geformten Schöpfraum eines Schraubenpumpenstators aufweist, ist die zuvor beschriebene Problemstellung gemäß Anspruch 13 durch den Einsatz entsprechend ausgestalteter Rotoren gelöst. Insoweit sind bevorzugte Ausgestaltungen und Weiterbildungen Gegenstand der weiteren Unteransprüche 14 und 15.With respect to a screw vacuum pump as a whole, which has two helical rotors in mutual contact engagement with each other in a suitably shaped pump chamber of a screw pump stator, the above-described problem according to
Zusammenfassend ergeben sich folgende Vorteile der Rotoren für kompakte Schraubenpumpen für Einsätze in Forschung und Industrie insbesondere mit chemisch aggressiven Stoffen:
- Eine effektive Kühlung des Rotors ist möglich.
- Der Rotor hat eine geringe Wärmeausdehnung.
- Die Rotorwelle hat eine ausreichend hohe Steifigkeit (E-Modul).
- Die Oberfläche des Rotors kann bei Verwendung eines passenden Werkstoffs für die Rotorhülle eine hohe chemische Beständigkeit aufweisen und berührungstolerant sein, also bei Berührung des Gegen-Schraubenrotors nicht zu Fressern neigen.
- Zur Verringerung potentieller Unwuchten kann der Rotor recht leicht sein.
- Die Fertigung des oft sehr anspruchsvollen und eng tolerierten Schraubenprofils wird bei Verwendung passender Werkstoffe für die Rotorhülle durch eine gute Bearbeitbarkeit des Materials des Rotors erleichtert.
- An effective cooling of the rotor is possible.
- The rotor has a low thermal expansion.
- The rotor shaft has a sufficiently high rigidity (modulus of elasticity).
- The surface of the rotor can have a high chemical resistance when using a suitable material for the rotor shell and be touch tolerant, so tend to prickers when touching the counter-screw rotor.
- To reduce potential imbalances, the rotor can be quite light.
- The production of the often very demanding and tightly tolerated screw profile is facilitated by using suitable materials for the rotor shell by a good machinability of the material of the rotor.
Ausgangspunkt der Erfindung ist die Erkenntnis, dass die Kühlung des Schraubenrotors bei kompakt bauenden Schraubenpumpen hauptsächlich durch Wärmeabfuhr über den Rotor und die Rotorwelle aus dem Schöpfraum heraus erfolgen muss, Erfindungsgemäß ist dafür vorgesehen, den Rotor mit einem Rotorkern aus einem hochwärmeleitfähigen Material aufzubauen, der von einer Rotorhülle, bevorzugt aus einem chemisch beständigen Kunststoff, umgeben ist. Als hochwärmeleitfähiges Material werden Materialien mit Wärmeleitfähigkeit von mehr als 100 W/m· K, vorzugsweise von mehr als 200 W/m · K, eingesetzt, also beispielsweise Aluminium oder Kupfer und einige Legierungen. Kunststoffe und Eisenlegierungen (Stahl, Gußeisen) erreichen diese Werte nicht und weisen keine ausreichende Wärmeableitung für eine effektive Kühlung der Rotors nach innen oder über die Rotorwelle auf.The starting point of the invention is the realization that the cooling of the screw rotor must be carried out with compact screw pumps mainly by heat dissipation through the rotor and the rotor shaft from the pump chamber out, according to the invention is provided to the rotor with a Build rotor core of a highly heat conductive material, which is surrounded by a rotor shell, preferably made of a chemically resistant plastic. Highly thermally conductive material used are materials having a thermal conductivity of more than 100 W / m.K, preferably more than 200 W / m.K, for example aluminum or copper and some alloys. Plastics and iron alloys (steel, cast iron) do not reach these values and do not have sufficient heat dissipation for effective cooling of the rotor inwards or over the rotor shaft.
In einer bevorzugten Ausführung besteht auch die Rotorwelle aus einem hochwärmeleitfähigen Material, so dass die Wärme vom Rotor über die Rotorwelle per Festkörper-Wärmeleitung aus dem Schöpfraum heraus transportiert wird. Besonders zweckmäßig ist es dabei, wenn die Rotorwelle mit dem Rotorkern einteilig ausgeführt ist, da dann die Festkörper-Wärmeleitung im Inneren des Rotorkerns ohne störende Grenzflächen bis in die Rotorwelle nach außen erfolgt,In a preferred embodiment, the rotor shaft is made of a highly heat-conductive material, so that the heat from the rotor via the rotor shaft by solid-state heat conduction is transported out of the pump chamber. It is particularly useful in this case if the rotor shaft with the rotor core is made in one piece, since then the solid state heat conduction takes place inside the rotor core without disturbing interfaces up to the rotor shaft to the outside,
In einer alternativen Ausführung wird für die Rotorwelle anstelle eines massiven hochwärmeleitfähigen Materials eine hohle Welle verwendet, durch die ein Kühlgas wie z.B. Luft gefördert wird, welches bevorzugt durch die Drehung der Welle selbst angesaugt wird, beispielsweise durch eine Art Gebläse auf einem freien Wellenende. Das Kühlgas wird durch die Rotorwellen bis in den Bereich der höchsten Wärmefreisetzung geleitet und kühlt dort den hochwärmeleitfähigen Rotorkern von innen. Das erhitzte Gas wird beispielsweise in den Auslass der Pumpe abgegeben und kann dort als Spülgas dienen, oder durch die Rotorwelle wieder zurück geführt. Auch in dieser Ausführung besteht der Rotor also aus einem hochwärmeleitfähigen Rotorker, der von einer Rotorhülle umgeben ist, wobei der Rotorkern in Kontakt mit der hohlen Rotorwelle oder direkt mit dem Kühlgas steht. Auch das Material der hohlen Rotorwelle kann hochwärmeleitfähig sein.In an alternative embodiment, a hollow shaft is used for the rotor shaft instead of a solid, highly heat-conductive material, through which a cooling gas such as e.g. Air is conveyed, which is preferably sucked by the rotation of the shaft itself, for example by a kind of blower on a free shaft end. The cooling gas is conducted through the rotor shafts into the area of the highest heat release and cools the highly heat-conductive rotor core from the inside. The heated gas is discharged, for example, into the outlet of the pump, where it can serve as purge gas, or guided back through the rotor shaft. Also in this embodiment, the rotor thus consists of a highly thermally conductive rotor core, which is surrounded by a rotor shell, wherein the rotor core is in contact with the hollow rotor shaft or directly with the cooling gas. The material of the hollow rotor shaft can also be highly heat-conductive.
Die Dicke des Umhüllungsmaterials, also der Rotorhülle, ergibt sich einerseits aus der Notwendigkeit, dass die Schicht diffusionsdicht und mechanisch stabil ist, und zum anderen daraus, dass die Wärmeleitung durch die Schicht zum Kernmaterial noch ausreichend hoch ist, um eine Überhitzung an der Oberfläche zu vermeiden. Erfindungsgemäß bedeutet dies, dass das hochwärmeleitfähige Kernmaterial in einer bevorzugten Ausführung bis in die Schraubengänge reicht, und nicht nur als im Wesentlichen zylindrisches Teil vorliegt. Das bedeutet, das hochwärmeleitfähige Material weist zumindest in diesem Abschnitt das Schraubenprofil (verringert um die Umhüllungswanddicke) auf, wobei das Umhüllungsmaterial in diesen Bereichen bevorzugt eine Dicke von 0.1 - 10 mm hat.The thickness of the cladding material, ie the rotor shell, results on the one hand from the need for the layer to be diffusion-tight and mechanically stable and, on the other hand, from the fact that the heat conduction through the layer to the core material is still sufficiently high to overheat the surface avoid. According to the invention, this means that the highly heat-conductive core material in a preferred embodiment extends into the screw threads, and is not only present as a substantially cylindrical part. This means that the highly heat-conductive material has at least in this section Screw profile (reduced by the sheath wall thickness), wherein the sheath material in these areas preferably has a thickness of 0.1 - 10 mm.
Obwohl die Rotorhülle oft nur eine vergleichsweise geringe spezifische Wärmeleitfähigkeit von meist < 5 W/m · K (typisch beispielsweise für Kunststoffe) aufweist, wird aufgrund der geringen Dicke der Rotorhülle eine ausreichende Wärmeableitung durch diese Schicht zum Rotorkern erzielt. Aus der Anwendung ergibt sich, dass der hochwärmeleitfähige Rotorkern bevorzugt im Bereich der höchsten Wärmefreisetzung, also am atmosphärenseitigen Ende des Rotors, in denen eine hohe Wärmeabfuhr durch den Rotor erforderlich ist, nach außen in die Schraubengänge reicht.Although the rotor shell often has only a comparatively low specific thermal conductivity of mostly <5 W / m · K (typically for plastics, for example), due to the small thickness of the rotor shell sufficient heat dissipation is achieved by this layer to the rotor core. From the application shows that the highly thermally conductive rotor core preferably in the region of the highest heat release, ie at the atmosphere-side end of the rotor, in which a high heat dissipation through the rotor is required, extends outward into the screw threads.
In einer bevorzugten Ausführungsform weist der erfindungsgemäße Rotor jedoch einen oder mehrere Abschnitte auf, in denen der hochwärmeleitfähige Rotorkern nicht oder nicht vollständig bis nach außen in die Schraubengänge reicht. Zur Erläuterung sollen mögliche Materialien für den Rotorkern und die Rotorhülle betrachtet werden.In a preferred embodiment, however, the rotor according to the invention has one or more sections in which the highly heat-conductive rotor core does not extend or not completely outwards into the screw threads. For explanation, possible materials for the rotor core and the rotor shell are considered.
Die Umhüllung eines Rotorkerns kann auf mehrere Arten erfolgen. Wird eine sehr dünne Beschichtung (< 0.1 mm) aufgetragen, kann auf eine mechanische Nacharbeit der Schicht unter Umständen verzichtet werden. Häufig sind solche Schichten aber nicht völlig diffusionsdicht, so dass die Schicht von den gepumpten Medien unterwandert werden kann und dann unter Vakuum abplatzt. Bei dickeren Beschichtungen muss die Schraubenprofilform aufwendig nachgearbeitet werden. Dickere Beschichtungen werden meist nach dem Auftrag (z.B. mittels elektrostatischer Pulverbeschichtung) aufgeschmolzen. Dies führt häufig zur Verrundung der Kanten, so dass sich nach der Endbearbeitung an Außenkanten Fehlstellen ergeben.The wrapping of a rotor core can be done in several ways. If a very thin coating (<0.1 mm) is applied, it may be possible to dispense with mechanical reworking of the layer. Often, however, such layers are not completely diffusion-tight, so that the layer can be infiltrated by the pumped media and then peeled off under vacuum. For thicker coatings, the screw profile form must be reworked consuming. Thicker coatings are usually melted after application (e.g., by electrostatic powder coating). This often leads to the rounding of the edges, resulting in defects after finishing on outer edges.
Von diesen Beschichtungsverfahren zu unterscheiden ist die Umspritzung eines Rotorkerns mit einem thermoplastischen Kunststoff. Bei diesem Verfahren läßt sich die Schichtdicke nahezu beliebig (also auch diffusionsdicht) wählen und die Kanten werden exakt ausgeformt. Gleichzeitig erlaubt dieses Verfahren, auch größere Kunststoffvolumina zu füllen.To be distinguished from these coating methods is the encapsulation of a rotor core with a thermoplastic material. In this method, the layer thickness can be almost arbitrary (ie, diffusion-tight) choose and the edges are accurately formed. At the same time, this method allows to fill even larger volumes of plastic.
Vergleicht man die mechanischen und thermischen Kennzahlen verschiedener Werkstoffe, so ergibt sich, dass von den Materialien mit sehr hoher Wärmeleitung von >100 W/m . K Kupfer und einige Kupferlegierungen als sehr geeignet erscheinen. Grund dafür sind die hohe Wärmeleitfähigkeit, die noch akzeptable Wärmeausdehnung und das noch akzeptable E-Modul. Aluminium und seine Legierungen zeigen bei allen drei Parametern deutlich schlechtere Werte, sind aber leichter. Aufgrund des deutlich geringeren E-Moduls eignet sich Aluminium nur schlecht als Rotorwellenmaterial, kann jedoch als Rotorkernmaterial eingesetzt werden, wobei die Rotorwelle dann aus einem anderen Material wie Kupfer oder aus einer Hohlwelle mit Gasinnenkühlung bestehen müsste. Zum Schutz korrosionsempfindlicher Materialien wie Kupfer können diese beschichtet werden, beispielsweise mit Ni, Cr, Ag oder Au.Comparing the mechanical and thermal characteristics of different materials, it follows that of the materials with very high heat conduction of> 100 W / m. K copper and some copper alloys as very appear appropriate. This is due to the high thermal conductivity, the still acceptable thermal expansion and the still acceptable modulus of elasticity. Aluminum and its alloys show significantly worse values for all three parameters but are lighter. Due to the significantly lower modulus of elasticity, aluminum is poorly suited as a rotor shaft material, but can be used as a rotor core material, the rotor shaft would then consist of a different material such as copper or a hollow shaft with internal gas cooling. To protect corrosion-sensitive materials such as copper, these can be coated, for example with Ni, Cr, Ag or Au.
Andere Metalle mit hoher Wärnneleitung wie Gold, Silber, Alkali- und Erdalkalimetalle, Zink, Molybdän oder Wolfram und ihre Legierungen scheiden wegen zu hoher Materialkosten, schlechter Bearbeitbarkeit, Reaktivität oder niedrigem E-Modul aus. Neuartige Materialien wie CFK weisen oft anisotrope und schwer beherrschbare Eigenschaften auf, insbesondere bei der Formung von Volumenkörpern. Zudem ist die Herstellung oft teuer und aufwendig. Auch spezielle Keramiken wie AlN weisen interessante Materialeigenschaften auf, sind jedoch schwer zu bearbeiten. Dennoch sind dies zukünftig interessante Materialien für den Rotorkern oder Teile des Rotorkerns von erfindungsgemäßen Rotoren.Other high thermal conductivity metals, such as gold, silver, alkali and alkaline earth metals, zinc, molybdenum or tungsten, and their alloys are eliminated because of excessive material costs, poor machinability, reactivity or low modulus of elasticity. Novel materials such as CFRP often exhibit anisotropic and difficult-to-control properties, especially in the formation of solids. In addition, the production is often expensive and expensive. Special ceramics such as AlN have interesting material properties, but are difficult to process. Nevertheless, in future these will be interesting materials for the rotor core or parts of the rotor core of rotors according to the invention.
Nachteilig an Kupfer sind das hohe spezifische Gewicht und die vergleichsweise hohen Materialkosten. Daher ist der zweite Aspekt der Erfindung, dass also das hochwärmeleitfähige Kernmaterial nur dort wo thermisch nötig, also insbesondere im Bereich der atrilosphärenseitigen Verdichtung, nach außen bis dicht unter die Kunststoffoberfläche reicht, besonders vorteilhaft. In anderen, thermisch weniger belasteten Bereichen des Rotors kann auf die Ausformung des Kernmaterials bis in die Schraubengänge hinein verzichtet werden und der Rotor kann dort aus einem relativ kleinen zylindrischen Rotorkern umgeben von Kunststoff als Rotorhülle bestehen.A disadvantage of copper is the high specific weight and the comparatively high material costs. Therefore, the second aspect of the invention, that is, that the highly thermally conductive core material only where thermally necessary, ie in particular in the area of the atrilosphärenenseitigen compression, outwardly to close under the plastic surface, particularly advantageous. In other, less thermally stressed areas of the rotor can be dispensed with the formation of the core material into the screw threads into it and the rotor can there consist of a relatively small cylindrical rotor core surrounded by plastic as a rotor shell.
Als Umhüllungsmaterial kommen bevorzugt chemisch hoch beständige Kunststoffe wie PPS, PEEK oder Fluorkunststoffe zum Einsatz, die bevorzugt mit Füllstoffen wie Kohle- oder Glasfaser verstärkt sind. Beispielsweise weist PEEK mit Kohlefaserverstärkung nur ca. 16% der Dichte von Kupfer auf. Damit läßt sich mit der erfindungsgemäßen Anordnung, wobei der hochwärmeleitfähige Kernmaterial nur dort wo thermisch nötig, also insbesondere im Bereich der atmosphärenseitigen Verdichtung, nach außen bis dicht unter die Kunststoffoberfläche reicht, das Gewicht des Schraubenrotors und somit potentielle Unwuchten erheblich verringern. Profilbedingte Unwuchten können bereits am Rotorkern weitgehend ausgeglichen werden, so dass am komplettierten Rotor nur noch kleine Korrekturen an der Rotorhülle erforderlich sind, wodurch auf großer Wuchtringe oder Bohrungen verzichtet werden kann.As sheathing material preferably chemically highly resistant plastics such as PPS, PEEK or fluoroplastics are used, which are preferably reinforced with fillers such as carbon or glass fiber. For example, PEEK with carbon fiber reinforcement only about 16% of the density of copper. Thus, with the arrangement according to the invention, wherein the highly thermally conductive core material only where thermally necessary, ie in particular in the region of the atmosphere-side compression, outwardly extends to close under the plastic surface, the weight of the screw rotor and thus significantly reduce potential imbalances. Profile-related imbalances can be largely compensated already on the rotor core, so that only small corrections to the rotor shell are required on the completed rotor, which can be dispensed with large balancing rings or holes.
Weitere Vorteile von Materialien wie PPS, PEEK oder Fluorkunststoffen sind die gute Bearbeitbarkeit und die Berührungstoleranz, also geringe Fresserneigung. Die Bearbeitung von solchen Kunststoffen ist erheblich einfacher, schneller und damit kostengünstiger als beispielsweise von hochkorrosionsfesten Edelstählen.Other advantages of materials such as PPS, PEEK or fluoroplastics are the good machinability and the contact tolerance, so little annoying tendency. The processing of such plastics is much easier, faster and therefore cheaper than, for example, highly corrosion-resistant stainless steels.
Die erfindungsgemäße Anordnung ergibt somit einen Rotor mit chemisch hochbeständiger und diffusionsdichter Oberfläche bei zugleich sehr hoher Wärmeleitung der Gesamtanordnung - zumindest im Bereich großer Wärmefreisetzung im Betrieb - bei überraschend günstigen Herstellkosten. Letzteres ergibt sich, da Werkstoffe wie Kupfer oder Aluminium nur dort eingesetzt werden wo nötig, materialsparende Fertigungsverfahren wie Spritzgießen angewandt werden, und die Materialien leicht bearbeitbar sind.The arrangement according to the invention thus provides a rotor with chemically highly resistant and diffusion-tight surface at the same time very high heat conduction of the overall arrangement - at least in the field of large heat release during operation - at surprisingly low production costs. The latter arises because materials such as copper or aluminum are used only where necessary, material-saving manufacturing processes such as injection molding are used, and the materials are easily editable.
Für die zuverlässige Anbindung der Rotorhülle an den Rotorkern ist eine formsehlüssige Verbindung möglichst mit Hinterschnitten zur Verzahnung nötig, falls keine ausreichende Materialhaftung erreichbar ist. Dazu können in den Rotorkern beispielsweise Nuten, Bohrungen oder Rillen eingebracht werden. Auch eine raue Oberfläche des Rotorkerns beispielsweise durch Sandstrahlen ist hilfreich.For the reliable connection of the rotor shell to the rotor core, a form-fit connection is necessary, if possible, with undercuts to the toothing, if sufficient material adhesion can not be achieved. For this purpose, for example, grooves, bores or grooves can be introduced into the rotor core. Even a rough surface of the rotor core, for example, by sandblasting is helpful.
Die Vorteile des erfindungsgemäßen Rotors werden in der bevorzugten Anordnung der Schraubenpumpe mit fliegend gelagerten Rotoren besonders deutlich. Bei fliegend gelagerten Rotoren wird der Lagerungs- und Antriebsbereich bevorzugt unter Umgebungsluftdruck und nicht in Kontakt mit den gepumpten Medien stehen. Damit dieser Lagerungs- und Antriebsbereich nicht mit einem Wellendichtring o.ä. zum Schöpfraum abgedichtet werden muss, wird die Druckseite des Pumpaggregats meist auf der Antriebsseite angeordnet werden.The advantages of the rotor according to the invention are particularly clear in the preferred arrangement of the screw pump with overhung rotors. In the case of overhung rotors, the storage and drive area is preferably under ambient air pressure and not in contact with the pumped media. So that this storage and drive area not with a shaft seal o.ä. must be sealed to the suction chamber, the pressure side of the pump unit is usually arranged on the drive side.
Dieser Bereich ist thermisch doppelt belastet, zum einen vom Motor, zum anderen von der Verdichtungswärme am atmosphärenseitigen Schraubenrotorende. Bei Einsatz hocheffizienter Synchronmotoren oder eines Getriebes und bei leistungsfähiger Kühlung des Antriebsbereichs beispielsweise mittels Gebläse ist der Antriebsbereich jedoch recht einfach auf niedriger Betriebstemperatur haltbar.This area is thermally loaded twice, on the one hand by the engine, on the other hand by the heat of compression at the atmosphere-side screw rotor end. When using highly efficient synchronous motors or a gearbox and with efficient cooling of the drive area, for example However, by means of a blower, the drive range is quite simply durable to a low operating temperature.
Die Abwärme aus der Verdichtung kann ein Vielfaches der Motorabwärme betragen. Der erfindungsgemäße Rotoraufbau erlaubt nun eine sehr effektive Ableitung der Verdichtungswärme aus dem Schöpfraum in Richtung des gut gekühlten Antriebsbereichs mit Hilfe der hochwärmeleitfähigen Rotorwelle aus einem Massivmaterial.The waste heat from the compression can be a multiple of the engine waste heat. The rotor assembly according to the invention now allows a very effective dissipation of the heat of compression from the pump chamber in the direction of the well-cooled drive range using the highly heat-conductive rotor shaft of a solid material.
In einer bevorzugten Ausführung sitzt im Antriebsbereich auf der Rotorwelle ein Mittel zur Abgabe dieser Wärme an die umgebende Luft. Dabei kann es sich beispielsweise um ein mitlaufendes Lüfterrad oder Scheiben beispielsweise aus Kupfer oder Aluminium handeln. Diese geben die Wärme von der Rotorwelle aufgrund der schnellen Rotation sehr effektiv an die Luft ab. Die erhitzte Luft kann durch einen von außen angelegten Kühlluftstrom abgeführt werden. Ein von einem mitlaufenden Lüfterrad erzeugter Luftstrom kann auch zur Kühlung des Motors dienen.In a preferred embodiment, a means for delivering this heat to the surrounding air is located in the drive region on the rotor shaft. This may be, for example, a revolving fan or discs, for example, copper or aluminum. These very effectively release the heat from the rotor shaft to the air due to the rapid rotation. The heated air can be removed by an externally applied cooling air flow. A generated by a follower fan air flow can also be used to cool the engine.
Gerade bei fliegender Lagerung der Rotoren ist es wichtig, am von den Lagern entfernten Ende der Rotoren möglichst geringe Massen zu haben. Große bewegte Massen weit entfernt von der Lagerung können schon bei geringer Unwucht zu großen Auslenkungen und damit Rotorkollisionen führen.Especially in the case of flying bearings of the rotors, it is important to have the smallest possible masses at the end of the rotors remote from the bearings. Large moving masses far away from the bearing can lead to large deflections and thus rotor collisions even with little imbalance.
Hier wird der zweite Aspekt der Erfindung besonders wichtig, gemäß der der hochwärmeleitfähige Rotorkern (mit oft hoher Dichte) außerhalb des thermisch hochbelasteten Teils des Rotors nicht bis dicht unter die Kunststoffoberfläche gezogen, sondern vielmehr möglichst weit reduziert wird. Dies verringert die bewegten Massen gerade am von der Lagerung entfernten Ende des Rotors erheblich.Here, the second aspect of the invention is particularly important according to which the highly thermally conductive rotor core (often with high density) outside the thermally highly stressed part of the rotor is not pulled close to the plastic surface, but rather is reduced as far as possible. This significantly reduces the moving masses, especially at the end of the rotor remote from the bearing.
Für die maßhaltige Bearbeitung der (in der Pumpe) fliegend gelagerten Rotoren ist je nach Fertigungsverfahren eine Aufnahme des Rotors in der Bearbeitungsmaschine auch auf der dem Lager abgewandten Seite erforderlich. Falls die Rotorhülle hierfür ungeeignet ist, kann der hochwärmeleitfähige Rotorkern stirnseitig auch auf der dem Lager abgewandten Seite nach außen geführt sein. Falls erforderlich, muss dieser Bereich später vor Korrosionsangriff geschützt werden, beispielsweise durch Abdeckung mit einem Stopfen beispielsweise aus PTFE. Alternativ kann die stirnseitige Aufnahme auch mit Hilfe eines hochkorrosionsfesten Metalls wie Hastelloy, welches fest mit dem Kernmaterial verbunden ist, erfolgen.Depending on the manufacturing process, a reception of the rotor in the processing machine is also required on the side facing away from the bearing for dimensionally stable machining of the rotors (in the pump). If the rotor shell is unsuitable for this, the highly thermally conductive rotor core can also be guided on the side facing away from the bearing to the outside. If necessary, this area must be protected later from corrosion attack, for example, by covering with a plug, for example made of PTFE. Alternatively, the frontal recording with Help a high corrosion resistant metal such as Hastelloy, which is firmly connected to the core material done.
In einer alternativen Ausprägung des erfindungsgemäßen Rotors für fliegende Lagerung ist der hochwärmeleitfähige Rotorkern und/oder die Rotorwelle nicht über die gesamte Länge des Schraubenrotors mit vollem Querschnitt vorhanden, oder hohl, oder fehlt völlig. Der der Lagerung abgewandte Teil des Rotors kann dann aus massivem Umhüllungsmaterial bestehen oder eine Ausnehmung aufweisen. Alle diese Ausprägungen führen zu einer deutlichen Verringerung der bewegten Massen im dem Lager fernen Bereich des Rotors.In an alternative embodiment of the rotor according to the invention for on-the-fly storage, the highly thermally conductive rotor core and / or the rotor shaft is not present over the entire length of the screw rotor with a full cross-section, or hollow, or completely absent. The part of the rotor facing away from the storage can then consist of solid wrapping material or have a recess. All these characteristics lead to a significant reduction of the moving masses in the bearing remote area of the rotor.
Die Herstellung des hochwärmeleitfähige Rotorkerns beispielsweise aus Kupfer oder Aluminium oder einer -legierung kann aus dem Vollen erfolgen, oder bevorzugt durch Befestigung einer hohlen Schraube auf einer Welle oder durch Verbindung einer Vollschraube mit einer kurzen Welle. Beides verringert den Materialaufwand für die Herstellung. In einer bevorzugten Ausführung mit noch geringerem Materialeinsatz ist der Rotorkern als Ganzes oder die hohle Schraube vorgegossen oder letztere besteht aus einem entsprechend gebogenen Metallblechteil.The production of the highly heat-conductive rotor core, for example, made of copper or aluminum or an alloy can be made from solid, or preferably by attaching a hollow screw on a shaft or by connecting a solid screw with a short shaft. Both reduce the cost of materials for the production. In a preferred embodiment with even less use of material, the rotor core as a whole or the hollow screw is precast or the latter consists of a correspondingly bent sheet metal part.
In einer weiteren bevorzugten Ausführungsform sind weitere Funktionselemente des Rotors in die Rotorhülle integriert. Dies können beispielsweise Wuchtgewichte auf einer oder beiden Seiten der Schraube sein, oder auch Spülgaslüfter, wie in
In einer weiteren bevorzugten Ausführungsform erfolgt der Antrieb der Schraubenpumpe durch einen Zwei-Wellen-Synchronantrieb, bestehend aus magnetisierten Zylindern auf jeder der beiden Rotorwellen, die durch ihre gegenseitige magnetische Wechselwirkung die Rotoren gegenläufig synchronisieren. Die beiden magnetisierten Zylinder sind von einer oder mehreren Wicklungen umgeben, die durch geeignete Bestromung wandernde Magnetfelder erzeugen, so dass sich die beiden magnetisierten Zylinder und damit die Rotorwellen gegenläufig synchron drehen.In a further preferred embodiment, the drive of the screw pump is effected by a two-shaft synchronous drive, consisting of magnetized cylinders on each of the two rotor shafts, which synchronize the rotors in opposite directions by their mutual magnetic interaction. The two magnetized cylinders are surrounded by one or more windings, which generate suitable magnetic field by moving current, so that the two magnetized cylinders and thus the rotor shafts rotate synchronously in opposite directions.
Im Folgenden wird die Erfindung nun anhand einer lediglich Ausführungsbeispiele darstellenden Zeichnung näher erläutert. In der Zeichnung zeigt
- Fig. 1
- einen erfindungsgemäßen Schraubenrotor für eine Schraubenvakuumpumpe im Schnitt und
- Fig. 2
- eine Schraubenvakuumpumpe mit zwei erfindungsgemäßen Rotoren im Schnitt.
- Fig. 1
- a screw rotor according to the invention for a screw vacuum pump in section and
- Fig. 2
- a screw vacuum pump with two rotors according to the invention in section.
Der in
Die Rotorhülle 4 umhüllt den Rotorkern 3 zumindest teilweise. Im in
Im dargestellten und bevorzugten Ausführungsbeispiel besteht der Rotorkern 3 aus einem Material, das eine hohe Wärmeleitfähigkeit von mehr als 100 W/m ·K aufweist, vorzugsweise eine Wärmeleitfähigkeit von mehr als 200 W/m · K. Auch die Rotorwelle 2 besteht bevorzugt aus einem Material, das eine hohe Wärmeleitfähigkeit aufweist, vorzugweise auch hier eine Wärmeleitfähigkeit von mehr als 100 W/m · K.In the illustrated and preferred embodiment, the
Alternativ oder zusätzlich kann die Rotorwelle 2 einen oder mehrere parallel zu ihrer Achse verlaufende Kanäle zur Zuführung von Gas in Richtung des Rotorkerns 3 aufweisen, so dass der Rotor 1 insgesamt von innen her gekühlt wird.Alternatively or additionally, the
Erfindungsgemäß kann der Rotorkern 3 in einzelnen Abschnitten des Rotors 1 bis in dessen Schraubengänge reichen wie das in
In weniger beanspruchten Bereichen kann der Rotorkern 3 ganz fehlen, die Rotorhülle 4 also den kompletten Rotor 1 außerhalb der Rotorwelle 2 bilden. Das sieht man in
Was die Rotorhülle 4 betrifft, so ist diese erfindungsgemäß vorzugsweise aus einem Material hergestellt, das eine im Vergleich mit der Wärmeleitfähigkeit des Rotorkerns 3 und der Rotorwelle 2 geringe Wärmeleitfähigkeit aufweist, vorzugsweise eine Wärmeleitfähigkeit von weniger als 5 W/m · K. Insbesondere empfiehlt sich hier, dass die Rotorhülle 4 aus Kunststoff, insbesondere aus einem thermoplastischen Kunststoff besteht. Bei entsprechenden Einsätzen für chemische Anwendungen empfiehlt es sich, den Kunststoff chemisch beständig auszuwählen, beispielsweise PPS, PEEK oder Fluorkunststoff. Die Festigkeit des Kunststoffes der Rotorhülle 4 kann durch Füllstoffe wie Glasfasern oder Kohlefasern erhöht werden.As regards the rotor shell 4, this invention is preferably made of a material which has a low thermal conductivity in comparison with the thermal conductivity of the
Vorzugsweise ist die Rotorhülle 4 in einem Spritzgußverfahren mit dem Rotorkern 3 verbunden, also auf diesen aufgebracht worden. Für den Rotorkern 3 oder Teile davon und/oder für die Rotorwelle 2 empfehlen sich als Werkstoffe Kupfer oder Aluminium oder Legierungen dieser Werkstoffe.Preferably, the rotor shell 4 is connected in an injection molding process with the
Demgegenüber sind die Rotoren 1, 1', die in der Schraubenvakuumpumpe von
Bei den Rotoren 1, 1' in
Die Rotoren 1, 1' in dem Ausführungsbeispiel von
In
Der Lagerungs- und Antriebsbereich liegt bevorzugt unter Umgebungsluftdruck. Er enthält Mittel zur Lagerung 12, 12'; 13, 13' der Rotoren 1, 1', sowie Mittel zur Synchronisation und/oder zum Antrieb der Rotoren 1, 1', Im hier dargestellten Beispiel bestehen letztere aus geeignet magnetisierten Zylindern 14, 14', die durch ihre gegenseitige magnetische Wechselwirkung die Rotoren 1, 1' gegenläufig synchronisieren. Die beiden magnetisierten Zylinder 14, 14' sind von einer oder mehreren Wicklungen 15, 15' umgeben, die durch geeignete Bestromung wandernde Magnetfelder erzeugen, so dass sich die beiden magnetisierten Zylinder 14, 14' und damit die Rotorwellen 2 der Rotoren 1, 1' gegenläufig synchron drehen. Der Antrieb der Schraubenvakuumpumpe ist also hier als Zwei-Wellen-Synchronantrieb 14, 14'; 15, 15' ausgeführt. Derartige Konstruktionen sind für sich aus dem Stand der Technik bekannt.The storage and drive range is preferably under ambient air pressure. It contains means for
Im Antriebsbereich sind auf der Welle Wärmeabgabemittel 16, 16' zur Abgabe von Wärme, die über die Rotorwellen 2 hierher geleitet wurde, an die umgebende Luft dargestellt. Dabei kann es sich beispielsweise um mitlaufende Lüfterräder oder Scheiben handeln, Die erhitzte Luft kann durch einen von außen angelegten Kühlluftstrom abgeführt werden (nicht dargestellt). Der vom mitlaufenden Wärmeabgabemittel 16, 16' erzeugte Luftstrom kann auch zur Kühlung des Antriebs 14, 14'; 15,15' dienen.In the drive region, heat emission means 16, 16 'for emitting heat, which has been conducted here via the
Zudem sind in
In dem in
Claims (15)
wobei der Rotor (1, 1') aus einer Rotorwelle (2), einem auf der Rotorwelle (2) sitzenden Rotorkern (3) und einer auf dem Rotorkern (3) sitzenden, den Rotorkern (3) zumindest teilweise umhüllenden Rotorhülle (4) besteht,
dadurch gekennzeichnet,
dass der Rotorkern (3) aus einem Material besteht, das eine Wärmeleitfähigkeit von mehr als 100 W/m · K, vorzugsweise eine Wärmeleitfähigkeit von mehr als 200 W/m · K, aufweist.Screw rotor for a screw vacuum pump, preferably for a screw vacuum pump with a pumping speed of less than 50 m 3 / h,
wherein the rotor (1, 1 ') comprises a rotor shaft (2), a rotor core (3) seated on the rotor shaft (2) and a rotor shell (4) which is seated on the rotor core (3) and at least partially surrounds the rotor core (3). consists,
characterized,
in that the rotor core (3) consists of a material which has a thermal conductivity of more than 100 W / m · K, preferably a thermal conductivity of more than 200 W / m · K.
dass die Rotorwelle (2) aus einem Material besteht, das eine hohe Wärmeleitfähigkeit, vorzugsweise eine Wärmeleitfähigkeit von mehr als 100 W/m · K, aufweist.Rotor according to claim 1, characterized in that
that the rotor shaft (2) consists of a material having a high thermal conductivity, preferably a thermal conductivity greater than 100 W / m · K.
dass die Rotorwelle (2) und der Rotorkern (3) einstückig ausgebildet sind.Rotor according to claim 2, characterized
that the rotor shaft (2) and the rotor core (3) are integrally formed.
dass die Rotorwelle (2) einen oder mehrere parallel zu ihrer Achse verlaufende Kanäle zur Zuführung von Gas in Richtung des Rotorkerns (3) aufweist.Rotor according to one of the preceding claims, characterized
that the rotor shaft (2) comprises one or more extending parallel to its axis channels for supplying gas in the direction of the rotor core (3).
dass der Rotorkern (3) zumindest abschnittsweise bis in die Schraubengänge des Rotors (1, 1') reicht, also hier gegenüber der Außenform des schraubenförmigen Rotors (1, 1') lediglich um die Dicke der Rotorhülle (4) in diesem Bereich verringerte Abmessungen aufweist, wobei, vorzugsweise, die Rotorhülle (4) in diesem Bereich eine Dicke von 0,1 mm bis 10 mm aufweist.Rotor according to one of the preceding claims, characterized
that the rotor core (3) at least in sections extends into the screw threads of the rotor (1, 1 '), thus here compared to the outer shape of the helical rotor (1, 1') only in this area reduced dimensions by the thickness of the rotor shell (4) , wherein, preferably, the rotor shell (4) in this area has a thickness of 0.1 mm to 10 mm.
dass der Rotorkern (3) nur in denjenigen Bereichen des Rotors (1, 1') bis in dessen Schraubengänge reicht, in denen im Betrieb des Rotors (1, 1') in einer Schraubenvakuumpumpe eine erhebliche Wärmeentwicklung auftritt, also vorzugsweise in einem Bereich des Rotors (1, 1'), der im Betrieb einem Auslass eines Schöpfraums zugewandt ist.Rotor according to claim 5, characterized in that
that the rotor core (3) extends only in those areas of the rotor (1, 1 ') into its screw threads, in which significant heat development occurs in a screw vacuum pump during operation of the rotor (1, 1'), ie preferably in a region of the Rotor (1, 1 '), which faces in operation to an outlet of a pump chamber.
dass die Rotorhülle (4) aus einem Material besteht, das eine im Vergleich mit der Wärmeleitfähigkeit des Rotorkerns (3) und der Rotorwelle (2) geringe Wärmeleitfähigkeit aufweist, vorzugsweise eine Wärmeleitfähigkeit von weniger als 5 W/m · K.Rotor according to one of the preceding claims, characterized
in that the rotor shell (4) consists of a material which has a low thermal conductivity in comparison with the thermal conductivity of the rotor core (3) and the rotor shaft (2), preferably a thermal conductivity of less than 5 W / m · K.
dass die Rotorhülle (4) aus Kunststoff, vorzugsweise aus einem thermoplastischen Kunststoff, besteht, wobei vorzugsweise, der Kunststoff ein chemisch beständiger Kunststoff wie PPS, PEEK oder Fluorkunststoff ist und/oder vorzugsweise, der Kunststoff mit einem Füllstoff wie Glasfasern oder Kohlefasern verstärkt ist,
wobei, vorzugsweise, die Rotorhülle (4) in einem Spritzgußverfahren auf dem Rotorkern (3) aufgebracht worden ist.Rotor according to claim 7, characterized
that the rotor shell (4) made of plastic, preferably is made of a thermoplastic material, preferably, of a chemically resistant plastic such as PPS, PEEK or fluorine plastic is plastic and / or, preferably, reinforced with a filler such as glass fibers or carbon fibers, plastic,
wherein, preferably, the rotor shell (4) has been applied in an injection molding process on the rotor core (3).
dass der Rotorhern (3) oder Teile davon und/oder die Rotorwelle (2) aus Kupfer oder Aluminium oder Legierungen dieser Werkstoffe besteht.Rotor according to claim 8, characterized in that
that the rotor core (3) or parts thereof and / or the rotor shaft (2) consists of copper or aluminum or alloys of these materials.
dass der Rotor (1, 1') für eine einseitige Lagerung an lediglich einem Ende der Rotorwelle (2) ausgestaltet ist.Rotor according to one of the preceding claims, characterized
that the rotor (1, 1 ') is designed for a one-sided mounting on only one end of the rotor shaft (2).
dass die Rotorwelle (2) und/oder der Rotorkern (3) im Bereich des von dem der Lagerung dienenden Ende abgewandten Ende des Rotors (1, 1') je nach dem Abstand von dem der Lagerung dienenden Ende einen verringerten Querschnitt aufweist, eine Ausnehmung aufweist oder völlig fehlt, wobei das gegenüber den vollständigen Außenabmessungen des Rotors (1, 1') fehlende Volumen durch die Rotorhülle (4) ausgefüllt ist.Rotor according to claim 10, characterized
that the rotor shaft (2) and / or the rotor core (3) in the region of the side remote from the serving of the bearing end of the rotor (1, 1 ') has a reduced cross-section depending on the distance from the serving to the end of storage, a recess has or is completely absent, wherein compared to the complete outer dimensions of the rotor (1, 1 ') missing volume is filled by the rotor shell (4).
dass auf der Rotorwelle (2) zwischen dem Rotorkern (3) und ggf, der Rotorhülle (4) und ihrem der Lagerung dienenden Ende ein Wärmeabgabemittel (16, 16') zur Wärmeabgabe an die Umgebungsatmosphäre angeordnet ist und/oder dass in die Rotorhülle (4) Funktionselemente (17, 17') integriert sind.Rotor according to one of the preceding claims, characterized
in that on the rotor shaft (2) between the rotor core (3) and optionally the rotor shell (4) and its end serving for storage, a heat-dissipating means (16, 16 ') is arranged for dissipating heat to the ambient atmosphere and / or that in the rotor shell ( 4) functional elements (17, 17 ') are integrated.
mit einem Schraubenpumpenstator (8) mit mindestens einem Einlass (10) und einem Auslass (11) und
mit zwei in gegenseitigem berührungslosern Eingriff stehenden schraubenförmigen Rotoren (1,1'), die in einem zu den Rotoren (1, 1') passend geformten Schöpfraum (9) des Schraubenpumpenstators (8) rotieren und dadurch ein gasförmiges Medium vom Einlass (10) zum Auslass (11) fördern,
gekennzeichnet durch
Rotoren (1, 1') nach einem oder mehreren der Ansprüche 1 bis 12.Screw vacuum pump, preferably with a pumping speed of less than 50 m 3 / h,
with a screw pump stator (8) having at least one inlet (10) and an outlet (11) and
with two helical rotors (1, 1 ') in mutual non-contact engagement, which rotate in a suction chamber (9) of the screw pump stator (8) suitably shaped in the rotors (1, 1'), thereby producing a gaseous medium from the inlet (10). to the outlet (11),
marked by
Rotors (1, 1 ') according to one or more of claims 1 to 12.
dass der Auslass (11) des Schöpfraums (9) an dem den gelagerten Enden der Rotoren (1, 1') zugewandten Ende des Schöpfraums (9) angeordnet ist.Screw vacuum pump according to claim 13, characterized in that
that the outlet (11) of the suction chamber (9) at the supported ends of the rotors (1, 1 ') facing the end of the suction chamber (9) is arranged.
dass zum Antrieb der Rotoren (1, 1') ein Zwei-Wellen-Synchronantrieb (14, 14'; 15, 15') vorgesehen ist.Screw vacuum pump according to claim 13 or 14, characterized
in that a two-shaft synchronous drive (14, 14 ', 15, 15') is provided for driving the rotors (1, 1 ').
Priority Applications (3)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP12000151.6A EP2615307B1 (en) | 2012-01-12 | 2012-01-12 | Screw vacuum pump |
US13/737,787 US20130183185A1 (en) | 2012-01-12 | 2013-01-09 | Screw rotor for a screw type vacuum pump |
CN2013100102284A CN103256224A (en) | 2012-01-12 | 2013-01-11 | Screw rotor for screw vacuum pump |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP12000151.6A EP2615307B1 (en) | 2012-01-12 | 2012-01-12 | Screw vacuum pump |
Publications (2)
Publication Number | Publication Date |
---|---|
EP2615307A1 true EP2615307A1 (en) | 2013-07-17 |
EP2615307B1 EP2615307B1 (en) | 2019-08-21 |
Family
ID=45531165
Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
---|---|---|---|
EP12000151.6A Active EP2615307B1 (en) | 2012-01-12 | 2012-01-12 | Screw vacuum pump |
Country Status (3)
Country | Link |
---|---|
US (1) | US20130183185A1 (en) |
EP (1) | EP2615307B1 (en) |
CN (1) | CN103256224A (en) |
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DE102016100957A1 (en) * | 2016-01-20 | 2017-07-20 | FRISTAM Pumpen Schaumburg GmbH | displacement |
DE202016005207U1 (en) * | 2016-08-30 | 2017-12-01 | Leybold Gmbh | Vacuum pump rotor |
DE202016005209U1 (en) * | 2016-08-30 | 2017-12-01 | Leybold Gmbh | Screw vacuum pump |
DE102016216279A1 (en) | 2016-08-30 | 2018-03-01 | Leybold Gmbh | Vacuum-screw rotor |
IT201800009944A1 (en) | 2018-10-31 | 2020-05-01 | Nova Rotors Srl | "VOLUMETRIC PUMP" |
WO2021197704A1 (en) * | 2020-03-31 | 2021-10-07 | Vacuubrand Gmbh + Co Kg | Electric motor and vacuum pump |
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CN206206150U (en) * | 2014-02-28 | 2017-05-31 | 凤凰计划股份有限公司 | The pump integral with two independent prime mover for driving |
CN107448384A (en) * | 2016-05-31 | 2017-12-08 | 苏州艾柏特精密机械有限公司 | Double-screw compressor rotor preparation method |
DE102017202356A1 (en) * | 2017-02-14 | 2018-08-16 | Bayerische Motoren Werke Aktiengesellschaft | Rotor shaft for an electric machine and electric machine |
US10491071B2 (en) * | 2017-02-16 | 2019-11-26 | General Electric Company | Method of manufacturing an electric machine with a conformal stator coating |
TWI624596B (en) * | 2017-03-15 | 2018-05-21 | 亞台富士精機股份有限公司 | Pump apparatus with remote monitoring function and pump apparatus monitoring system |
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FR3076582B1 (en) * | 2018-01-09 | 2020-01-24 | Pfeiffer Vacuum | DRY TYPE VACUUM PUMP AND METHOD FOR CONTROLLING A SYNCHRONOUS VACUUM PUMP MOTOR |
DE102018130472A1 (en) * | 2018-11-30 | 2020-06-04 | Nidec Gpm Gmbh | Screw pump |
BE1027047B1 (en) * | 2019-02-12 | 2020-09-10 | Atlas Copco Airpower Nv | Screw rotor and method of manufacturing such screw rotor |
WO2021161067A1 (en) | 2020-02-12 | 2021-08-19 | Nova Rotors Srl | Positive displacement pump |
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Also Published As
Publication number | Publication date |
---|---|
CN103256224A (en) | 2013-08-21 |
EP2615307B1 (en) | 2019-08-21 |
US20130183185A1 (en) | 2013-07-18 |
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