EP3507497B1 - Vacuum pump screw rotor - Google Patents

Vacuum pump screw rotor Download PDF

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Publication number
EP3507497B1
EP3507497B1 EP17749704.7A EP17749704A EP3507497B1 EP 3507497 B1 EP3507497 B1 EP 3507497B1 EP 17749704 A EP17749704 A EP 17749704A EP 3507497 B1 EP3507497 B1 EP 3507497B1
Authority
EP
European Patent Office
Prior art keywords
vacuum pump
screw
displacer
elements
recess
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
EP17749704.7A
Other languages
German (de)
French (fr)
Other versions
EP3507497A1 (en
Inventor
Thomas Dreifert
Dirk Schiller
Wolfgang Giebmanns
Roland Müller
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.)
Leybold GmbH
Original Assignee
Leybold GmbH
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Filing date
Publication date
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Publication of EP3507497A1 publication Critical patent/EP3507497A1/en
Application granted granted Critical
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    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08Rotary-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
    • F04C18/12Rotary-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
    • F04C18/14Rotary-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
    • F04C18/18Rotary-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 similar tooth forms
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C18/00Rotary-piston pumps specially adapted for elastic fluids
    • F04C18/08Rotary-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
    • F04C18/12Rotary-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
    • F04C18/14Rotary-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
    • F04C18/16Rotary-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
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C25/00Adaptations of pumps for special use of pumps for elastic fluids
    • F04C25/02Adaptations of pumps for special use of pumps for elastic fluids for producing high vacuum
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2210/00Fluid
    • F04C2210/10Fluid working
    • F04C2210/1005Air
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2210/00Fluid
    • F04C2210/22Fluid gaseous, i.e. compressible
    • F04C2210/221Air
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2220/00Application
    • F04C2220/10Vacuum
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2230/00Manufacture
    • F04C2230/10Manufacture by removing material
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2240/00Components
    • F04C2240/20Rotors
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2240/00Components
    • F04C2240/30Casings or housings
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C2250/00Geometry
    • F04C2250/20Geometry of the rotor
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F04POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
    • F04CROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT MACHINES FOR LIQUIDS; ROTARY-PISTON, OR OSCILLATING-PISTON, POSITIVE-DISPLACEMENT PUMPS
    • F04C23/00Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids
    • F04C23/001Combinations of two or more pumps, each being of rotary-piston or oscillating-piston type, specially adapted for elastic fluids; Pumping installations specially adapted for elastic fluids; Multi-stage pumps specially adapted for elastic fluids of similar working principle
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2210/00Working fluid
    • F05B2210/10Kind or type
    • F05B2210/12Kind or type gaseous, i.e. compressible
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2210/00Working fluid
    • F05B2210/16Air or water being indistinctly used as working fluid, i.e. the machine can work equally with air or water without any modification
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2230/00Manufacture
    • F05B2230/10Manufacture by removing material
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2240/00Components
    • F05B2240/20Rotors
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2280/00Materials; Properties thereof
    • F05B2280/10Inorganic materials, e.g. metals
    • F05B2280/102Light metals
    • F05B2280/1021Aluminium
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05BINDEXING SCHEME RELATING TO WIND, SPRING, WEIGHT, INERTIA OR LIKE MOTORS, TO MACHINES OR ENGINES FOR LIQUIDS COVERED BY SUBCLASSES F03B, F03D AND F03G
    • F05B2280/00Materials; Properties thereof
    • F05B2280/10Inorganic materials, e.g. metals
    • F05B2280/1073Aluminium alloy, e.g. AlCuMgPb
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05CINDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2201/00Metals
    • F05C2201/02Light metals
    • F05C2201/021Aluminium
    • FMECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
    • F05INDEXING SCHEMES RELATING TO ENGINES OR PUMPS IN VARIOUS SUBCLASSES OF CLASSES F01-F04
    • F05CINDEXING SCHEME RELATING TO MATERIALS, MATERIAL PROPERTIES OR MATERIAL CHARACTERISTICS FOR MACHINES, ENGINES OR PUMPS OTHER THAN NON-POSITIVE-DISPLACEMENT MACHINES OR ENGINES
    • F05C2201/00Metals
    • F05C2201/90Alloys not otherwise provided for
    • F05C2201/903Aluminium alloy, e.g. AlCuMgPb F34,37

Definitions

  • the invention relates to a vacuum pump screw rotor.
  • Screw vacuum pumps such as in EP1 890 039 described, have two rotor elements in a pumping chamber formed by a housing.
  • the rotor elements have a helical contour and are rotated in opposite directions to convey gases.
  • the displacement element of the rotor element i.e. the helical contour
  • the pitch On the inlet side or suction side, the pitch is large and the volume of the chambers formed per turn is also large. The pitch decreases in the direction of the outlet, so that on the outlet or pressure side there is a small pitch and also small chamber volumes per turn.
  • the object of the invention is to create a vacuum pump screw rotor that can be produced cost-effectively with low power consumption and low thermal load on the pump. Furthermore, the object of the invention is to create a corresponding screw vacuum pump and a suitable manufacturing method.
  • the object is achieved according to the invention by a vacuum pump screw rotor according to claim 1, a vacuum pump according to claim 10, and a manufacturing method according to claim 14.
  • the vacuum pump screw rotor according to the invention has at least two helical displacement elements arranged on a rotor shaft.
  • the rotor element is formed by the displacement elements.
  • the at least two displacement elements have different pitches, with the pitch being constant for each displacement element.
  • the vacuum pump screw rotor according to the invention has two displacement elements, with a first suction-side displacement element having a larger constant pitch and a second pressure-side displacement element having a smaller constant pitch.
  • each displacement element has at least one helical recess which has the same contour over its entire length.
  • the contours are preferably different for each displacement element.
  • the individual displacement element therefore preferably has a constant pitch and a consistent contour. This simplifies production considerably, so that production costs can be greatly reduced.
  • the contour of the helical recess of the suction-side displacement element i.e. in particular the first displacement element in the pumping direction, is asymmetrical. Due to the asymmetrical design of the contour or profile, the flanks can be designed in such a way that the leakage areas, the so-called blow holes, in particular disappear completely or at least have a small cross-section.
  • a particularly suitable asymmetrical profile is the so-called "Quimby profile". Although such a profile is relatively difficult to produce, it has the advantage that there is no continuous blow hole. A short circuit only occurs between two adjacent chambers. Since this is an asymmetrical profile with different profile flanks, at least two work steps are required for production, since the two flanks have to be produced in different work steps due to their asymmetry.
  • the pressure-side displacement element in particular the last displacement element in the pumping direction, is provided with a symmetrical contour of the helical recess.
  • the symmetrical contour has the particular advantage that it is easier to manufacture.
  • both flanks with a symmetrical contour can be manufactured in one work step using a rotating end mill or a rotating disk mill.
  • Such symmetrical profiles only have small blow holes, but these are continuous, i.e. not just provided between two adjacent chambers. The size of the blow hole decreases when the pitch is reduced.
  • such symmetrical profiles can be provided in particular in the pressure-side displacement element, since in a preferred embodiment this has a smaller pitch than the suction-side displacement element and preferably also than the displacement elements arranged between the suction-side and pressure-side displacement elements.
  • the tightness of such symmetrical profiles is somewhat lower, they have the advantage that they are significantly easier to manufacture.
  • a particularly suitable symmetrical profile is the so-called "cycloid profile".
  • the provision of at least two such displacement elements means that the corresponding screw vacuum pump can generate low inlet pressures with low power consumption.
  • the thermal load is also low.
  • the arrangement of at least two displacement elements designed according to the invention with a constant pitch and consistent contour in a vacuum pump leads to essentially the same results as with a vacuum pump with a displacement element with a changing pitch. With high installed volume ratios, three or four displacement elements can be provided per rotor.
  • a pressure-side displacement element i.e. in particular the last displacement element in the pumping direction, has a large number of turns.
  • a large number of turns means that a larger gap between the screw rotor and the housing can be accepted while maintaining the same performance.
  • the gap can have a cold gap width of 0.1 - 0.3 mm.
  • a large number of outlet turns or number of turns in the pressure-side displacement element can be produced inexpensively because, according to the invention, this displacement element has a constant pitch and in particular also a symmetrical contour. This enables simple and inexpensive production, so that the provision of a larger number of turns is acceptable.
  • This pressure-side or last displacement element preferably has more than 8, in particular more than 10 and particularly preferably more than 12 turns.
  • the use of symmetrical profiles has the advantage in a particularly preferred embodiment that both flanks of the profile can be cut simultaneously with one milling cutter. In this case, the Milling cutter through the opposite flank, so that deformation or bending of the milling cutter during the milling process and the resulting inaccuracies are avoided.
  • displacement elements and the rotor shaft are formed in one piece.
  • the change in pitch between adjacent displacement elements is discontinuous or abrupt.
  • the two displacement elements are arranged at a distance from one another in the longitudinal direction, so that a circumferential cylindrical ring-shaped chamber is formed between two displacement elements, which serves as a tool outlet. This is particularly advantageous in the case of rotors formed in one piece, since the tool producing the helical line can be easily guided out in this area. If the displacement elements are manufactured independently of one another and then mounted on a shaft, the provision of a tool outlet, in particular such an annular cylindrical area, is not necessary.
  • no tool outlet is provided between two adjacent displacement elements at the pitch change.
  • both flanks preferably have a defect or recess in order to be able to guide the tool out.
  • Such a defect has no significant influence on the compression performance of the pump, since it is a very localized defect or recess.
  • the vacuum pump screw rotor according to the invention has in particular several displacement elements. These can each have the same or different diameters. It is preferred that the The pressure-side displacement element has a smaller diameter than the suction-side displacement element.
  • displacement elements manufactured independently of the rotor shaft, these are mounted on the shaft using press fits, for example. It is preferred to provide elements such as dowel pins to determine the angular position of the displacement elements relative to one another.
  • the screw rotor in the case of a one-piece design of the screw rotor, but also in the case of a multi-piece design, it is preferred to manufacture it from aluminum or an aluminum alloy. It is particularly preferred to manufacture the rotor from aluminum or an aluminum alloy, in particular AlSi7Mg or AISi17Cu4Mg.
  • the alloy preferably has a high silicon content of preferably more than 15% in order to reduce the coefficient of expansion.
  • the aluminum used has a low coefficient of expansion. It is preferred if the material has a coefficient of expansion of less than 18 * 10 -6 / K.
  • the surface of the displacement elements is coated, in particular a coating against wear and/or corrosion is provided. In this case, it is preferred to provide an anodic or another suitable coating depending on the area of application.
  • the invention further relates to a screw vacuum pump.
  • This has two intermeshing vacuum pump screw rotors as described above.
  • the two screw rotors are arranged in a suction chamber formed by a pump housing.
  • one of the two screw rotors is connected to a drive device such as an electric motor.
  • the two screw rotors can be connected to one another via gears, which are arranged in particular on the rotor shafts. This also results in synchronization of the counter-rotating screw rotors.
  • Such a high internal compression is possible in particular due to the design of the two rotors with at least two compression elements, each with a constant pitch and in particular also a constant contour, with a high number of turns of the pressure-side displacement element.
  • This is particularly possible although large gaps are permitted in the area of the pressure-side displacement element.
  • the large gaps have the particular advantage that the thermal load is distributed more evenly over the pressure-side displacement element.
  • the thermal expansion of the corresponding displacement element and thus the risk of the displacement element touching the inside of the housing is also avoided.
  • the screw rotors have a lower expansion coefficient than the housing.
  • the expansion coefficient of the housing is at least 5%, and particularly preferably at least 10% greater than that of the screw rotors.
  • the housing is made of an aluminum alloy with a lower silicon content than the silicon content in the material of the screw rotors. This ensures a higher thermal expansion of the housing compared to the screw rotors. This ensures in particular that during operation, i.e. with increasing thermal load, the gap can become smaller, but that a sufficient gap always remains between the outside of the displacement elements and the inside of the suction chamber.
  • the invention relates to a method for producing a screw rotor as described above.
  • the production takes place in particular such that the displacement elements and the rotor shaft are formed in one piece.
  • a base body for the screw rotor is provided.
  • the helical recesses for producing the displacement element are produced using a form milling cutter such as a finger milling cutter or disc milling cutter. This is done in a separate step for each displacement element, since the pitch and in particular the contour of the helical recesses are different for each displacement element.
  • the recess is made with a single tool, in particular in a single operation. Furthermore, it is preferred that the tool reproduces the outer contour of the recess so that the production of preferably both flanks can be carried out in one work step. In the case of the asymmetrical part, the flanks must be machined by two different tools.
  • a tool run-out is produced before the helical recesses are produced.
  • a ring-cylindrical recess can be produced by milling or turning.
  • no such tool run-out is provided. Instead, a recess or defect is provided in a flank of an adjacent displacement element. The defect or recess is created when the milling cutter is guided out.
  • the base body used is in particular cylindrical, so that the rotor shaft with any shaft journals connected to it and in particular the displacement elements can be manufactured from a single base body. It is also possible to use a base body that is designed as a semi-finished product and already has recesses and/or bearing journals.
  • the base body can be manufactured using a casting process, for example.
  • the rotor has two displacement elements 10, 12.
  • a first suction-side displacement element 10 has a large pitch of approximately 50 - 150 mm/revolution. The pitch is constant over the entire displacement element 10.
  • the contour of the helical recess is also constant.
  • the second pressure-side displacement element 12 has a constant pitch and a constant contour of the recess over its length.
  • the pitch of the pressure-side displacement element 12 is preferably in the range of 10 - 30 mm/revolution.
  • a ring-cylindrical recess 14 is provided between the two displacement elements. This serves to ensure that the one-piece design of the Fig.1 A tool run-out is realized in the screw rotor shown.
  • the one-piece screw rotor has two bearing seats 16 and a shaft end 18.
  • a gear wheel for driving, for example, is connected to the shaft end 18.
  • the two displacement elements 10, 12 are manufactured separately and then fixed to a rotor shaft 20, for example by pressing. This manufacture is somewhat more complex, but the cylindrical distance 14 between two adjacent displacement elements 10, 12 is not required as a tool run-out.
  • the bearing seats 16 and the shaft ends 18 can be an integral part of the displacement elements.
  • a continuous shaft 20 can be manufactured from a different material than the displacement elements 10, 12.
  • Fig.3 shows a schematic sectional view of an asymmetrical profile (e.g. a Quimby profile).
  • the asymmetrical profile shown is a so-called "Quimby profile”.
  • the sectional view shows two screw rotors that mesh with each other and whose longitudinal direction is perpendicular to the plane of the drawing.
  • the opposing rotation of the rotors is indicated by the two arrows 15.
  • the profiles of the flanks 19 and 21 are designed differently for each rotor.
  • the opposing flanks 19, 21 must therefore be manufactured independently of each other. Although this is somewhat more complex and difficult to manufacture, it has the advantage that there is no continuous blow hole, but rather just a short circuit between two adjacent chambers.
  • Such an asymmetrical profile is preferably provided in the suction-side displacement element 10.
  • FIG.4 shows a cross-section of two displacement elements or two screw rotors, which in turn rotate in opposite directions (arrows 15).
  • the flanks 23 of each displacement element are symmetrical.
  • the preferred embodiment of a symmetrically designed contour shown is a cycloid profile.
  • a symmetrical profile, as in Fig.4 shown, is preferably provided on the pressure-side displacement elements 12.
  • FIG.5 The embodiment shown is again a one-piece design.
  • a recess or defect is provided in the flank of the displacement element 12 to guide the tool, such as a milling cutter, out.
  • displacement elements can also have different head diameters and corresponding foot diameters. It is preferred that a displacement element with a larger head diameter is arranged at the inlet, i.e. on the suction side, in order to achieve a greater suction capacity in this area and/or to increase the built-in volume ratio. Combinations of the embodiments described above are also possible.
  • one or more displacement elements can be manufactured in one piece with the shaft or an additional displacement element can be manufactured independently of the shaft and then mounted on the shaft.
  • a schematic sectional view of a vacuum pump ( Fig.5 ) shows two vacuum pump screw rotors 26 arranged in a suction chamber 24 in a housing 22.
  • the two rotors are mounted in the housing via bearings 28.
  • Gears 32 are connected to each of the two shaft ends 18. These mesh with each other so that synchronization of the two shafts is ensured.
  • One of the two gears 32 is connected to a drive device such as an electric motor.
  • the gas is sucked in in the area of the suction-side displacement elements 10, as shown by an arrow 34.
  • the gas is expelled accordingly as shown by an arrow 36 at the end of the second, pressure-side displacement element 12.

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  • Engineering & Computer Science (AREA)
  • Mechanical Engineering (AREA)
  • General Engineering & Computer Science (AREA)
  • Applications Or Details Of Rotary Compressors (AREA)
  • Rotary Pumps (AREA)

Description

Die Erfindung betrifft einen Vakuumpumpen-Schraubenrotor.The invention relates to a vacuum pump screw rotor.

Schrauben-Vakuumpumpen, wie beispielsweise in EP 1 890 039 beschrieben, weisen in einem von einem Gehäuse ausgebildeten Schöpfraum zwei Rotorelemente auf. Die Rotorelemente weisen eine schraubenlinienförmige Kontur auf und werden zum Fördern von Gasen gegenläufig gedreht. Zur Erzielung einer hohen inneren Verdichtung, das heißt eines Volumenverhältnisses zwischen dem Einlass und dem Auslass der Pumpe ist es bekannt, dass das Verdrängerelement des Rotorelements, das heißt die schraubenlinienförmige Kontur eine sich ändernde Steigung aufweist. Auf der Einlassseite bzw. saugseitig ist die Steigung groß und das Volumen der ausgebildeten Kammern je Windung ebenfalls groß. Die Steigung nimmt in Richtung des Auslasses ab, so dass auslass- bzw. druckseitig eine geringe Steigung und auch geringe Kammer-Volumen je Windung ausgebildet sind. Durch Vorsehen einer veränderlichen Steigung kann eine geringe Leistungsaufnahme bei niedrigen Einlassdrücken und gleichzeitig eine geringe thermische Belastung der Pumpe realisiert werden. Das Vorsehen von sich ändernder Steigung erfordert einen aufwendigen und daher teuren Herstellungsprozess. Insbesondere muss das Herstellen wie das Fräsen oder Drehen der Windungen, d.h. der schraubenlinienförmigen Ausnehmungen in mehreren aufeinanderfolgenden Arbeitsschritten erfolgen.Screw vacuum pumps, such as in EP1 890 039 described, have two rotor elements in a pumping chamber formed by a housing. The rotor elements have a helical contour and are rotated in opposite directions to convey gases. In order to achieve a high internal compression, i.e. a volume ratio between the inlet and the outlet of the pump, it is known that the displacement element of the rotor element, i.e. the helical contour, has a changing pitch. On the inlet side or suction side, the pitch is large and the volume of the chambers formed per turn is also large. The pitch decreases in the direction of the outlet, so that on the outlet or pressure side there is a small pitch and also small chamber volumes per turn. By providing a variable pitch, low power consumption at low inlet pressures and at the same time low thermal load on the pump can be achieved. Providing a changing pitch requires a complex and therefore expensive manufacturing process. In particular, the manufacturing process such as milling or turning the turns, i.e. the helical recesses, must be carried out in several successive work steps.

Aufgabe der Erfindung ist es, einen Vakuumpumpen-Schraubenrotor zu schaffen, der bei geringer Leistungsaufnahme und geringer thermischer Belastung der Pumpe kostengünstig herzustellen ist. Ferner ist es Aufgabe der Erfindung eine entsprechende Schraubenvakuumpumpe sowie ein geeignetes Herstellungsverfahren zu schaffen.The object of the invention is to create a vacuum pump screw rotor that can be produced cost-effectively with low power consumption and low thermal load on the pump. Furthermore, the object of the invention is to create a corresponding screw vacuum pump and a suitable manufacturing method.

Die Lösung der Aufgabe erfolgt erfindungsgemäß durch einen Vakuumpumpen-Schraubenrotor gemäß Anspruch 1, eine Vakuumpumpe gemäß Anspruch 10, sowie ein Herstellungsverfahren gemäß Anspruch 14.The object is achieved according to the invention by a vacuum pump screw rotor according to claim 1, a vacuum pump according to claim 10, and a manufacturing method according to claim 14.

Der erfindungsgemäße Vakuumpumpen-Schraubenrotor weist mindestens zwei auf einer Rotorwelle angeordnete schraubenlinienförmige Verdrängungselemente auf. Durch die Verdrängungselemente ist das Rotorelement ausgebildet. Die mindestens zwei Verdrängungselemente weisen erfindungsgemäß unterschiedliche Steigungen auf, wobei je Verdrängungselement die Steigung konstant ist. Beispielsweise weist der erfindungsgemäße Vakuumpumpen-Schraubenrotor zwei Verdrängungselemente auf, wobei ein erstes saugseitiges Verdrängungselement eine größere konstante Steigung und ein zweites druckseitiges Verdrängungselement eine kleinere konstante Steigung aufweist. Durch das erfindungsgemäße Vorsehen von mehreren Verdrängungselementen, die jeweils eine konstante Steigung aufweisen, ist die Herstellung erheblich vereinfacht.The vacuum pump screw rotor according to the invention has at least two helical displacement elements arranged on a rotor shaft. The rotor element is formed by the displacement elements. According to the invention, the at least two displacement elements have different pitches, with the pitch being constant for each displacement element. For example, the vacuum pump screw rotor according to the invention has two displacement elements, with a first suction-side displacement element having a larger constant pitch and a second pressure-side displacement element having a smaller constant pitch. By providing several displacement elements according to the invention, each of which has a constant pitch, production is considerably simplified.

Erfindungsgemäß weist jedes Verdrängungselement mindestens eine schraubenlinienförmige Ausnehmung auf, die über ihre gesamte Länge dieselbe Kontur aufweist. Die Konturen sind vorzugsweise je Verdrängungselement unterschiedlich. Das einzelne Verdrängungselement weist somit vorzugsweise eine konstante Steigung und eine gleichbleibende Kontur auf. Dies vereinfacht die Herstellung erheblich, so dass die Herstellungskosten stark gesenkt werden können.According to the invention, each displacement element has at least one helical recess which has the same contour over its entire length. The contours are preferably different for each displacement element. The individual displacement element therefore preferably has a constant pitch and a consistent contour. This simplifies production considerably, so that production costs can be greatly reduced.

Zur weiteren Verbesserung der Saugleistung ist die Kontur der schraubenlinienförmigen Ausnehmung des saugseitigen Verdrängungselements, das heißt insbesondere des in Pumprichtung ersten Verdrängungselements asymmetrisch ausgebildet. Durch die asymmetrische Ausbildung der Kontur bzw. des Profils können die Flanken derart ausgestaltet werden, dass die Leckageflächen, die sogenannten Blaslöcher insbesondere vollständig verschwinden oder zumindest einen geringen Querschnitt aufweisen. Ein besonders geeignetes asymmetrisches Profil ist das sogenannte "Quimby-Profil". Ein derartiges Profil ist zwar relativ schwierig herzustellen, weist jedoch den Vorteil auf, dass kein durchgehendes Blasloch vorhanden ist. Ein Kurzschluss ist nur zwischen zwei benachbarten Kammern gegeben. Da es sich um ein asymmetrisches Profil mit unterschiedlichen Profilflanken handelt, sind für die Herstellung zumindest zwei Arbeitsschritte erforderlich, da die beiden Flanken aufgrund ihrer Asymmetrie in unterschiedlichen Arbeitsschritten hergestellt werden müssen.To further improve the suction performance, the contour of the helical recess of the suction-side displacement element, i.e. in particular the first displacement element in the pumping direction, is asymmetrical. Due to the asymmetrical design of the contour or profile, the flanks can be designed in such a way that the leakage areas, the so-called blow holes, in particular disappear completely or at least have a small cross-section. A particularly suitable asymmetrical profile is the so-called "Quimby profile". Although such a profile is relatively difficult to produce, it has the advantage that there is no continuous blow hole. A short circuit only occurs between two adjacent chambers. Since this is an asymmetrical profile with different profile flanks, at least two work steps are required for production, since the two flanks have to be produced in different work steps due to their asymmetry.

Das druckseitige Verdrängungselement, insbesondere das in Pumprichtung letzte Verdrängungselement, ist mit einer symmetrischen Kontur der schraubenlinienförmigen Ausnehmung versehen.The pressure-side displacement element, in particular the last displacement element in the pumping direction, is provided with a symmetrical contour of the helical recess.

Die symmetrische Kontur hat insbesondere den Vorteil, dass die Herstellung einfacher ist. Insbesondere können beide Flanken mit symmetrischer Kontur durch einen rotierenden Fingerfräser oder durch einen rotierenden Scheibenfräser in einem Arbeitsschritt hergestellt werden. Derartige symmetrische Profile weisen nur kleine Blaslöcher auf, diese sind jedoch durchgehend, d.h. nicht nur zwischen zwei benachbarten Kammern vorgesehen. Die Größe des Blaslochs verringert sich bei Verringerung der Steigung. Insofern können derartige symmetrische Profile insbesondere bei dem druckseitigen Verdrängungselement vorgesehen werden, da diese in bevorzugter Ausführungsform eine kleinere Steigung als das saugseitige Verdrängungselement und vorzugsweise auch als das zwischen dem saugseitigen und dem druckseitigen Verdrängungselement angeordnete Verdrängungselemente aufweist. Wenngleich die Dichtigkeit derartiger symmetrischer Profile etwas geringer ist, weisen diese den Vorteil auf, dass die Herstellung deutlich einfacher ist. Insbesondere ist es möglich, das symmetrische Profil in einem einzigen Arbeitsschritt und vorzugsweise mit einem einfachen Fingerfräser oder Scheibenfräser herzustellen. Dies reduziert die Kosten erheblich. Ein besonders geeignetes symmetrisches Profil ist das sogenannte "Zykloiden-Profil".The symmetrical contour has the particular advantage that it is easier to manufacture. In particular, both flanks with a symmetrical contour can be manufactured in one work step using a rotating end mill or a rotating disk mill. Such symmetrical profiles only have small blow holes, but these are continuous, i.e. not just provided between two adjacent chambers. The size of the blow hole decreases when the pitch is reduced. In this respect, such symmetrical profiles can be provided in particular in the pressure-side displacement element, since in a preferred embodiment this has a smaller pitch than the suction-side displacement element and preferably also than the displacement elements arranged between the suction-side and pressure-side displacement elements. Although the tightness of such symmetrical profiles is somewhat lower, they have the advantage that they are significantly easier to manufacture. In particular, it is possible to produce the symmetrical profile in a single work step and preferably with a simple end mill or disc mill. This reduces costs considerably. A particularly suitable symmetrical profile is the so-called "cycloid profile".

Das Vorsehen mindestens zweier derartiger Verdrängungselemente führt dazu, dass die entsprechende Schraubenvakuumpumpe bei geringer Leistungsaufnahme niedrige Einlassdrücke erzeugen kann. Auch ist die thermische Belastung gering. Das Anordnen von mindestens zwei erfindungsgemäß ausgestalteten Verdrängungselementen mit konstanter Steigung und gleichbleibender Kontur in einer Vakuumpumpe führt zu im Wesentlichen gleichen Ergebnissen, wie bei einer Vakuumpumpe mit einem Verdrängungselement mit sich ändernder Steigung. Bei hohen eingebauten Volumenverhältnissen können je Rotor drei oder vier Vedrängungselemente vorgesehen werden.The provision of at least two such displacement elements means that the corresponding screw vacuum pump can generate low inlet pressures with low power consumption. The thermal load is also low. The arrangement of at least two displacement elements designed according to the invention with a constant pitch and consistent contour in a vacuum pump leads to essentially the same results as with a vacuum pump with a displacement element with a changing pitch. With high installed volume ratios, three or four displacement elements can be provided per rotor.

Zur Verringerung des erzielbaren Einlassdrucks und/oder zur Verringerung der Leistungsaufnahme und/oder der thermischen Belastung weist bei einer besonders bevorzugten Ausführungsform ein druckseitiges, das heißt insbesondere in Pumprichtung letztes Verdrängungselement eine große Anzahl an Windungen auf. Durch eine hohe Anzahl an Windungen kann ein größerer Spalt zwischen dem Schraubenrotor und dem Gehäuse akzeptiert werden bei gleichbleibender Performance. Der Spalt kann hierbei eine Kalt-Spaltweite von 0,1 - 0,3 mm aufweisen. Eine große Anzahl an Auslasswindungen bzw. Anzahl an Windungen bei dem druckseitigen Verdrängungselement ist kostengünstig herstellbar, da erfindungsgemäß dieses Verdrängungselement eine konstante Steigung und insbesondere auch eine symmetrische Kontur aufweist. Hierdurch ist eine einfache und kostengünstige Herstellung möglich, so dass das Vorsehen einer größeren Anzahl an Windungen akzeptabel ist. Vorzugsweise weist dieses druckseitige bzw. letzte Verdrängungselement mehr als 8, insbesondere mehr als 10 und besonders bevorzugt mehr als 12 Windungen auf. Das Verwenden symmetrischer Profile hat in besonders bevorzugter Ausführungsform den Vorteil, dass beide Flanken des Profils mit einem Fräser gleichzeitig geschnitten werden können. Hierbei erfolgt zusätzlich ein Abstützen des Fräsers durch die jeweils gegenüberliegende Flanke, so dass ein Verformen bzw. Verbiegen des Fräsers während des Fräsvorgangs und hierdurch hervorgerufene Ungenauigkeiten vermieden sind.In order to reduce the achievable inlet pressure and/or to reduce the power consumption and/or the thermal load, in a particularly preferred embodiment, a pressure-side displacement element, i.e. in particular the last displacement element in the pumping direction, has a large number of turns. A large number of turns means that a larger gap between the screw rotor and the housing can be accepted while maintaining the same performance. The gap can have a cold gap width of 0.1 - 0.3 mm. A large number of outlet turns or number of turns in the pressure-side displacement element can be produced inexpensively because, according to the invention, this displacement element has a constant pitch and in particular also a symmetrical contour. This enables simple and inexpensive production, so that the provision of a larger number of turns is acceptable. This pressure-side or last displacement element preferably has more than 8, in particular more than 10 and particularly preferably more than 12 turns. The use of symmetrical profiles has the advantage in a particularly preferred embodiment that both flanks of the profile can be cut simultaneously with one milling cutter. In this case, the Milling cutter through the opposite flank, so that deformation or bending of the milling cutter during the milling process and the resulting inaccuracies are avoided.

Zur weiteren Reduzierung der Herstellungskosten ist es besonders bevorzugt, die Verdrängungselemente und die Rotorwelle einstückig auszubilden.To further reduce manufacturing costs, it is particularly preferred to form the displacement elements and the rotor shaft in one piece.

Bei einer weiteren bevorzugten Ausführungsform ist der Steigungswechsel zwischen benachbarten Verdrängungselementen unstetig bzw. sprunghaft ausgebildet. Gegebenenfalls sind die beiden Verdrängungselemente in Längsrichtung in einem Abstand zueinander angeordnet, so dass zwischen zwei Verdrängungselementen eine umlaufende zylinderringförmige Kammer ausgebildet ist, die als Werkzeugauslauf dient. Dies ist insbesondere bei einstückig ausgebildeten Rotoren vorteilhaft, da das die Schraubenlinie herstellende Werkzeug in diesem Bereich auf einfache Weise herausgeführt werden kann. Sofern die Verdrängungselemente unabhängig voneinander hergestellt und sodann auf einer Welle montiert werden, ist das Vorsehen eines Werkzeugauslaufs, insbesondere eines derartigen ringzylindrischen Bereichs nicht erforderlich.In a further preferred embodiment, the change in pitch between adjacent displacement elements is discontinuous or abrupt. If necessary, the two displacement elements are arranged at a distance from one another in the longitudinal direction, so that a circumferential cylindrical ring-shaped chamber is formed between two displacement elements, which serves as a tool outlet. This is particularly advantageous in the case of rotors formed in one piece, since the tool producing the helical line can be easily guided out in this area. If the displacement elements are manufactured independently of one another and then mounted on a shaft, the provision of a tool outlet, in particular such an annular cylindrical area, is not necessary.

Bei einer bevorzugten Weiterbildung der Erfindung ist zwischen zwei benachbarten Verdrängungselementen am Steigungswechsel kein Werkzeugauslauf vorgesehen. In dem Bereich des Steigungswechsels weisen vorzugsweise beide Flanken eine Fehlstelle bzw. Ausnehmung auf, um das Werkzeug herausführen zu können. Eine derartige Fehlstelle hat keinen nennenswerten Einfluss auf die Verdichtungsleistung der Pumpe, da es sich um eine örtlich stark begrenzte Fehlstelle bzw. Ausnehmung handelt.In a preferred development of the invention, no tool outlet is provided between two adjacent displacement elements at the pitch change. In the area of the pitch change, both flanks preferably have a defect or recess in order to be able to guide the tool out. Such a defect has no significant influence on the compression performance of the pump, since it is a very localized defect or recess.

Der erfindungsgemäße Vakuumpumpen-Schraubenrotor weist insbesondere mehrere Verdrängungselemente auf. Diese können jeweils den gleichen oder unterschiedliche Durchmesser aufweisen. Bevorzugt ist es hierbei, dass das druckseitige Verdrängungselement einen kleineren Durchmesser als das saugseitige Verdrängungselement aufweist.The vacuum pump screw rotor according to the invention has in particular several displacement elements. These can each have the same or different diameters. It is preferred that the The pressure-side displacement element has a smaller diameter than the suction-side displacement element.

Bei unabhängig von der Rotorwelle hergestellten Verdrängungselementen werden diese beispielsweise durch Presspassungen auf der Welle montiert. Hierbei ist es bevorzugt, Elemente wie Passstifte zur Festlegung der Winkelposition der Verdrängungselemente zueinander vorzusehen.In the case of displacement elements manufactured independently of the rotor shaft, these are mounted on the shaft using press fits, for example. It is preferred to provide elements such as dowel pins to determine the angular position of the displacement elements relative to one another.

Insbesondere bei der einstückigen Ausgestaltung des Schraubenrotors aber auch bei einer mehrstückigen Ausgestaltung ist es bevorzugt, diesen aus Aluminium oder aus einer Aluminiumlegierung herzustellen. Besonders bevorzugt ist es, den Rotor aus Aluminium oder einer Aluminium-Legierung insbesondere AlSi7Mg oder AISi17Cu4Mg herzustellen. Die Legierung hat vorzugsweise einen hohen Silicium-Anteil von vorzugsweise mehr als 15 %, um den Ausdehnungskoeffizienten zu verringern.In particular, in the case of a one-piece design of the screw rotor, but also in the case of a multi-piece design, it is preferred to manufacture it from aluminum or an aluminum alloy. It is particularly preferred to manufacture the rotor from aluminum or an aluminum alloy, in particular AlSi7Mg or AISi17Cu4Mg. The alloy preferably has a high silicon content of preferably more than 15% in order to reduce the coefficient of expansion.

Das verwendete Aluminium weist in einer weiteren bevorzugten Weiterbildung der Erfindung einen geringen Ausdehnungskoeffizienten auf. Bevorzugt ist es, wenn das Material einen Ausdehnungskoeffizienten von weniger als 18 * 10-6/K aufweist. In einer weiter bevorzugten Ausführungsform ist die Oberfläche der Verdrängungselemente beschichtet, wobei insbesondere eine Beschichtung gegen Verschleiß und/oder Korrosion vorgesehen ist. Hierbei ist es bevorzugt eine anodische oder eine andere geeignete Beschichtung je nach Anwendungsgebiet vorzusehen.In a further preferred development of the invention, the aluminum used has a low coefficient of expansion. It is preferred if the material has a coefficient of expansion of less than 18 * 10 -6 / K. In a further preferred embodiment, the surface of the displacement elements is coated, in particular a coating against wear and/or corrosion is provided. In this case, it is preferred to provide an anodic or another suitable coating depending on the area of application.

Des Weiteren betrifft die Erfindung eine Schraubenvakuumpumpe. Diese weist zwei miteinander kämmende Vakuumpumpen-Schraubenrotoren wie vorstehend beschrieben auf. Die beiden Schraubenrotoren sind in einem von einem Pumpengehäuse ausgebildeten Schöpfraum angeordnet. Üblicherweise ist eine der beiden Schraubenrotoren mit einer Antriebseinrichtung wie einem Elektromotor verbunden. Die beiden Schraubenrotoren können über Zahnräder, die insbesondere auf den Rotorwellen angeordnet sind, miteinander verbunden sein. Hierdurch erfolgt ferner eine Synchronisation der sich gegenläufig drehenden Schraubenrotoren. In besonders bevorzugter Ausführungsform ist es insbesondere aufgrund der erfindungsgemäßen Ausgestaltung der Schraubenrotoren möglich, eine innere Verdichtung der Schraubenvakuumpumpe von mindestens zwei insbesondere mindestens vier zu erzielen. Eine derart hohe innere Verdichtung ist insbesondere aufgrund der Ausgestaltung der beiden Rotoren mit mindestens zwei Verdichtungselementen mit jeweils konstanter Steigung und insbesondere auch konstanter Kontur bei ferner hoher Windungsanzahl des druckseitigen Verdrängungselements möglich. Dies ist insbesondere möglich, obwohl im Bereich des druckseitigen Verdrängungselements große Spalte zugelassen werden. Die großen Spalte weisen insbesondere den Vorteil auf, dass die thermische Belastung gleichmäßiger auf das druckseitige Verdrängungselement verteilt wird. Insbesondere ist auch die thermische Ausdehnung des entsprechenden Verdrängungselements und somit die Gefahr des Berührens des Verdrängungselements an der Innenseite des Gehäuses vermieden. Ein weiterer diesbezüglicher Aspekt besteht darin, dass die Schraubenrotoren einen geringeren Ausdehnungskoeffizienten als das Gehäuse aufweisen. Insbesondere ist der Ausdehnungskoeffizient des Gehäuses mindestens 5%, und besonders bevorzugt mindestens 10% größer als derjenige der Schraubenrotoren.The invention further relates to a screw vacuum pump. This has two intermeshing vacuum pump screw rotors as described above. The two screw rotors are arranged in a suction chamber formed by a pump housing. Usually, one of the two screw rotors is connected to a drive device such as an electric motor. The two screw rotors can be connected to one another via gears, which are arranged in particular on the rotor shafts. This also results in synchronization of the counter-rotating screw rotors. In a particularly preferred embodiment, it is possible, in particular due to the inventive design of the screw rotors, to achieve an internal compression of the screw vacuum pump of at least two, in particular at least four. Such a high internal compression is possible in particular due to the design of the two rotors with at least two compression elements, each with a constant pitch and in particular also a constant contour, with a high number of turns of the pressure-side displacement element. This is particularly possible although large gaps are permitted in the area of the pressure-side displacement element. The large gaps have the particular advantage that the thermal load is distributed more evenly over the pressure-side displacement element. In particular, the thermal expansion of the corresponding displacement element and thus the risk of the displacement element touching the inside of the housing is also avoided. Another aspect in this regard is that the screw rotors have a lower expansion coefficient than the housing. In particular, the expansion coefficient of the housing is at least 5%, and particularly preferably at least 10% greater than that of the screw rotors.

Bevorzugt ist es hierbei, dass das Gehäuse aus einer Aluminiumlegierung mit geringerem Siliciumanteil als der Siliciumanteil in dem Material der Schraubenrotoren hergestellt ist. Hierdurch ist eine höhere thermische Ausdehnung des Gehäuses gegenüber den Schraubenrotoren sichergestellt. Hierdurch ist insbesondere sichergestellt, dass im Betrieb, d.h. bei steigender thermischer Belastung, der Spalt zwar geringer werden kann, jedoch stets ein ausreichender Spalt zwischen der Außenseite der Verdrängungselemente und der Innenseite des Schöpfraums verbleibt.It is preferred that the housing is made of an aluminum alloy with a lower silicon content than the silicon content in the material of the screw rotors. This ensures a higher thermal expansion of the housing compared to the screw rotors. This ensures in particular that during operation, i.e. with increasing thermal load, the gap can become smaller, but that a sufficient gap always remains between the outside of the displacement elements and the inside of the suction chamber.

Des Weiteren betrifft die Erfindung ein Verfahren zur Herstellung eines Schraubenrotors wie vorstehend beschreiben. Die Herstellung erfolgt hierbei insbesondere derart, dass die Verdrängungselemente und die Rotorwelle einstückig ausgebildet sind. In einem ersten Schritt wird ein Grundkörper für den Schraubenrotor bereitgestellt. Die schraubenlinienförmigen Ausnehmungen zur Herstellung des Verdrängungselements werden mittels eines Formfräsers wie eines Fingerfräsers oder Scheibenfräsers hergestellt. Dies erfolgt je Verdrängungselement in einem gesonderten Schritt, da die Steigung und insbesondere die Kontur der schraubenlinienförmigen Ausnehmungen je Verdrängungselement unterschiedlich sind.Furthermore, the invention relates to a method for producing a screw rotor as described above. The production takes place in particular such that the displacement elements and the rotor shaft are formed in one piece. In a first step, a base body for the screw rotor is provided. The helical recesses for producing the displacement element are produced using a form milling cutter such as a finger milling cutter or disc milling cutter. This is done in a separate step for each displacement element, since the pitch and in particular the contour of the helical recesses are different for each displacement element.

Bevorzugt ist es, dass bei Verdrängungselementen mit symmetrischer Kontur die Ausnehmung mit einem einzigen Werkzeug insbesondere in einem einzigen Arbeitsgang erfolgt. Des Weiteren ist es bevorzugt, dass das Werkzeug die Außenkontur der Ausnehmung abbildet, so dass die Herstellung vorzugsweise beider Flanken in einem Arbeitsschritt erfolgen kann. Beim asymmetrischen Teil müssen die Flanken von zwei verschiedenen Werkzeugen bearbeitet werden.It is preferred that in displacement elements with a symmetrical contour the recess is made with a single tool, in particular in a single operation. Furthermore, it is preferred that the tool reproduces the outer contour of the recess so that the production of preferably both flanks can be carried out in one work step. In the case of the asymmetrical part, the flanks must be machined by two different tools.

Bevorzugt ist es, dass insbesondere bei einstückig hergestellten Schraubenrotoren vor der Herstellung der schraubenlinienförmigen Ausnehmungen ein Werkzeugauslauf hergestellt wird. Eine derartige ringzylindrische Ausnehmung kann durch Fräsen oder Drehen hergestellt werden.It is preferred that, particularly in the case of screw rotors manufactured in one piece, a tool run-out is produced before the helical recesses are produced. Such a ring-cylindrical recess can be produced by milling or turning.

In einer besonders bevorzugten Weiterbildung wird kein derartiger Werkzeugauslauf vorgesehen. Stattdessen wird in einer Flanke eines benachbarten Verdrängungselements eine Ausnehmung bzw. Fehlstelle vorgesehen. Hierbei entsteht die Fehlstelle bzw. Ausnehmung beim Herausführen des Fräsers.In a particularly preferred development, no such tool run-out is provided. Instead, a recess or defect is provided in a flank of an adjacent displacement element. The defect or recess is created when the milling cutter is guided out.

Der verwendete Grundkörper ist insbesondere zylindrisch ausgebildet, so dass aus einem einzigen Grundkörper die Rotorwelle mit sich daran gegebenenfalls anschließenden Wellenzapfen sowie insbesondere auch die Verdrängungselemente hergestellt werden können. Ebenso ist es möglich, einen Grundkörper zu verwenden, der als Halbzeug ausgebildete ist und bereits Ausnehmungen und/oder Lagerzapfen aufweist. Die Herstellung des Grundkörpers kann beispielsweise im Gussverfahren erfolgen.The base body used is in particular cylindrical, so that the rotor shaft with any shaft journals connected to it and in particular the displacement elements can be manufactured from a single base body. It is also possible to use a base body that is designed as a semi-finished product and already has recesses and/or bearing journals. The base body can be manufactured using a casting process, for example.

Nachfolgend wird die Erfindung anhand einer bevorzugten Ausführungsform unter Bezugnahme auf die anliegenden Zeichnungen näher erläutert.The invention is explained in more detail below using a preferred embodiment with reference to the accompanying drawings.

Es zeigen:

Fig. 1
eine schematische Draufsicht einer ersten bevorzugten Ausführungsform eines Vakuumpumpen-Schraubenrotors,
Fig. 2
eine schematische Draufsicht einer zweiten bevorzugten Ausführungsform eines Vakuumpumpen-Schraubenrotors,
Fig. 3
eine schematische Schnittansicht von Verdrängungselementen mit asymmetrischem Profil,
Fig. 4
eine schematische Schnittansicht von Verdrängungselementen mit symmetrischem Profil und
Fig. 5
eine schematische Schnittansicht einer Schrauben-Vakuumpumpe.
Show it:
Fig.1
a schematic plan view of a first preferred embodiment of a vacuum pump screw rotor,
Fig.2
a schematic plan view of a second preferred embodiment of a vacuum pump screw rotor,
Fig.3
a schematic sectional view of displacement elements with asymmetric profile,
Fig.4
a schematic sectional view of displacement elements with symmetrical profile and
Fig.5
a schematic sectional view of a screw vacuum pump.

Bei der ersten bevorzugten Ausführungsform des Vakuumpumpen-Schraubenrotors weist der Rotor zwei Verdrängungselemente 10, 12 auf. Ein erstes saugseitiges Verdrängungselement 10 weist eine große Steigung von ca. 50 - 150 mm/Umdrehung auf. Die Steigung ist über das gesamte Verdrängungselement 10 konstant. Auch die Kontur der schraubenlinienförmigen Ausnehmung ist konstant. Das zweite druckseitige Verdrängungselement 12 weist über seine Länge wiederum eine konstante Steigung und eine konstante Kontur der Ausnehmung auf. Die Steigung des druckseitigen Verdrängungselements 12 liegt vorzugsweise im Bereich von 10 - 30 mm/Umdrehung. Zwischen den beiden Verdrängungselementen ist eine ringzylindrische Ausnehmung 14 vorgesehen. Diese dient dazu, das aufgrund der einstückigen Ausgestaltung des in Fig. 1 dargestellten Schraubenrotors ein Werkzeugauslauf realisiert ist.In the first preferred embodiment of the vacuum pump screw rotor, the rotor has two displacement elements 10, 12. A first suction-side displacement element 10 has a large pitch of approximately 50 - 150 mm/revolution. The pitch is constant over the entire displacement element 10. The contour of the helical recess is also constant. The second pressure-side displacement element 12 has a constant pitch and a constant contour of the recess over its length. The pitch of the pressure-side displacement element 12 is preferably in the range of 10 - 30 mm/revolution. Between A ring-cylindrical recess 14 is provided between the two displacement elements. This serves to ensure that the one-piece design of the Fig.1 A tool run-out is realized in the screw rotor shown.

Ferner weist der einstückig ausgebildete Schraubenrotor zwei Lagersitze 16 und ein Wellenende 18 auf. Mit dem Wellenende 18 wird beispielsweise ein Zahnrad zum Antrieb verbunden.Furthermore, the one-piece screw rotor has two bearing seats 16 and a shaft end 18. A gear wheel for driving, for example, is connected to the shaft end 18.

Bei der in Fig. 2 dargestellten zweiten bevorzugten Ausführungsform sind die beiden Verdrängungselemente 10, 12 gesondert hergestellt und sodann auf einer Rotorwelle 20 beispielsweise durch Aufpressen fixiert. Diese Herstellung ist zwar etwas aufwendiger, jedoch ist der zylindrische Abstand 14 zwischen zwei benachbarten Verdrängungselementen 10, 12 als Werkzeugauslauf nicht erforderlich. Die Lagersitze 16 und die Wellenenden 18 können integraler Bestandteil der Verdrängungselemente sein. Alternativ kann eine durchgehende Welle 20, auch aus einem anderen sich von den Verdrängungselementen 10, 12 unterscheidenden Werkstoff, hergestellt sein.At the Fig.2 In the second preferred embodiment shown, the two displacement elements 10, 12 are manufactured separately and then fixed to a rotor shaft 20, for example by pressing. This manufacture is somewhat more complex, but the cylindrical distance 14 between two adjacent displacement elements 10, 12 is not required as a tool run-out. The bearing seats 16 and the shaft ends 18 can be an integral part of the displacement elements. Alternatively, a continuous shaft 20 can be manufactured from a different material than the displacement elements 10, 12.

Fig. 3 zeigt eine schematische Schnittansicht eines asymmetrischen Profils (z.B. ein Quimby-Profil). Bei dem dargestellten asymmetrischen Profil handelt es sich um ein sogenanntes "Quimby-Profil". Die Schnittansicht zeigt zwei Schraubenrotoren, die miteinander kämmen und deren Längsrichtung senkrecht zur Zeichenebene ist. Die gegenläufige Drehung der Rotoren ist durch die beiden Pfeile 15 angedeutet. Bezogen auf eine senkrecht zur Längsachse der Verdrängungselemente verlaufenden Ebene 17 sind die Profile der Flanken 19 und 21 je Rotor unterschiedlich ausgestaltet. Die einander gegenüberliegenden Flanken 19, 21 müssen somit unabhängig voneinander hergestellt werden. Die daher zwar etwas aufwändigere und schwierigere Herstellung hat jedoch den Vorteil, dass kein durchgehendes Blasloch vorhanden ist, sondern lediglich zwischen zwei benachbarten Kammern ein Kurzschluss besteht. Fig.3 shows a schematic sectional view of an asymmetrical profile (e.g. a Quimby profile). The asymmetrical profile shown is a so-called "Quimby profile". The sectional view shows two screw rotors that mesh with each other and whose longitudinal direction is perpendicular to the plane of the drawing. The opposing rotation of the rotors is indicated by the two arrows 15. In relation to a plane 17 running perpendicular to the longitudinal axis of the displacement elements, the profiles of the flanks 19 and 21 are designed differently for each rotor. The opposing flanks 19, 21 must therefore be manufactured independently of each other. Although this is somewhat more complex and difficult to manufacture, it has the advantage that there is no continuous blow hole, but rather just a short circuit between two adjacent chambers.

Ein derartiges asymmetrisches Profil ist vorzugsweise bei dem saugseitigen Verdrängungselement 10 vorgesehen.Such an asymmetrical profile is preferably provided in the suction-side displacement element 10.

Die schematische Schnittansicht in Fig. 4 zeigt wiederum einen Querschnitt zweier Verdrängungselemente bzw. zweier Schraubenrotoren, die wiederum gegenläufig rotieren (Pfeile 15). Bezogen auf die Symmetrieachse 17 sind die Flanken 23 je Verdrängungselement symmetrisch ausgebildet. Bei dem in Fig. 4 dargestellten bevorzugten Ausführungsbeispiel einer symmetrisch ausgestalteten Kontur handelt es sich um ein Zykloiden-Profil.The schematic sectional view in Fig.4 shows a cross-section of two displacement elements or two screw rotors, which in turn rotate in opposite directions (arrows 15). In relation to the axis of symmetry 17, the flanks 23 of each displacement element are symmetrical. In the Fig.4 The preferred embodiment of a symmetrically designed contour shown is a cycloid profile.

Ein symmetrisches Profil, wie in Fig. 4 dargestellt, ist vorzugsweise bei den druckseitigen Verdrängungselementen 12 vorgesehen.A symmetrical profile, as in Fig.4 shown, is preferably provided on the pressure-side displacement elements 12.

Bei der weiteren in Fig. 5 dargestellten Ausführungsform handelt es sich wieder um eine einstückige Ausgestaltung. Zum Herausführen des Werkzeugs, wie eines Fingerfräsers ist in der Flanke des Verdrängungselements 12 eine Ausnehmung bzw. Fehlstelle vorgesehen.In the further Fig.5 The embodiment shown is again a one-piece design. A recess or defect is provided in the flank of the displacement element 12 to guide the tool, such as a milling cutter, out.

Ferner ist es möglich, dass mehr als zwei Verdrängungselemente vorgesehen sind. Diese können ggf. auch unterschiedliche Kopfdurchmesser und entsprechende Fußdurchmesser aufweisen. Hierbei ist es bevorzugt, dass ein Verdrängungselement mit größerem Kopfdurchmesser am Einlass, d.h. saugseitig angeordnet ist, um in diesem Bereich ein größeres Saugvermögen zu realisieren und/ oder das eingebaute Volumenverhältnis zu vergrößern. Ferner sind Kombinationen der vorstehend beschriebenen Ausführungsformen möglich. Beispielsweise können ein oder mehrere Verdrängungselemente einstückig mit der Welle oder ein zusätzliches Verdrängungselement unabhängig von der Welle hergestellt und sodann auf der Welle montiert werden.It is also possible for more than two displacement elements to be provided. These can also have different head diameters and corresponding foot diameters. It is preferred that a displacement element with a larger head diameter is arranged at the inlet, i.e. on the suction side, in order to achieve a greater suction capacity in this area and/or to increase the built-in volume ratio. Combinations of the embodiments described above are also possible. For example, one or more displacement elements can be manufactured in one piece with the shaft or an additional displacement element can be manufactured independently of the shaft and then mounted on the shaft.

Eine schematische Schnittansicht einer Vakuumpumpe (Fig. 5) zeigt in einem Gehäuse 22 zwei in einem Schöpfraum 24 angeordnete Vakuumpumpen-Schraubenrotoren 26. Die beiden Rotoren sind über Lager 28 im Gehäuse gelagert. Mit zwei Wellenenden 18 sind jeweils Zahnräder 32 verbunden. Diese kämmen miteinander, so dass eine Synchronisation der beiden Wellen gewährleistet ist. Eines der beiden Zahnräder 32 ist mit einer Antriebseinrichtung wie einem Elektromotor verbunden.A schematic sectional view of a vacuum pump ( Fig.5 ) shows two vacuum pump screw rotors 26 arranged in a suction chamber 24 in a housing 22. The two rotors are mounted in the housing via bearings 28. Gears 32 are connected to each of the two shaft ends 18. These mesh with each other so that synchronization of the two shafts is ensured. One of the two gears 32 is connected to a drive device such as an electric motor.

Wie aus Fig. 5 ersichtlich ist, erfolgt das Einsaugen des Gases im Bereich der saugseitigen Verdrängungselemente 10, wie durch einen Pfeil 34 dargestellt. Das Ausstoßen des Gases erfolgt entsprechend wie durch einen Pfeil 36 dargestellt am Ende des zweiten, druckseitigen Verdrängungselementes 12.As from Fig.5 As can be seen, the gas is sucked in in the area of the suction-side displacement elements 10, as shown by an arrow 34. The gas is expelled accordingly as shown by an arrow 36 at the end of the second, pressure-side displacement element 12.

Claims (19)

  1. A vacuum pump screw rotor, comprising
    at least two helical displacer elements (10, 12) arranged on a rotor shaft, wherein the at least two displacer elements (10, 12) have pitches differing from each other but being constant for each displacer element, and
    wherein the displacer elements (10, 12) each comprise at least one helical recess, each recess having a uniform contour over its entire length,
    characterized in
    that the helical recess of a suction-side displacer element (10) has an asymmetric contour, and
    that the helical recess of a pressure-side displacer element (12) has a symmetric contour.
  2. The vacuum pump screw rotor according to claim 1, characterized in that at least two rotor elements comprising respective helical displacer elements are provided, wherein the displacer elements have pitches differing from each other but being constant for each displacer element.
  3. The vacuum pump screw rotor according to claim 1 or 2, characterized in that the pressure-side displacer element (10) comprises more than 8, preferably more than 10 and with particular preference more than 12 windings.
  4. The vacuum pump screw rotor according to any one of claims 1 to 3, characterized in that a pressure-side displacer element is of the single-threaded type.
  5. The vacuum pump screw rotor according to any one of claims 1 to 4, characterized in that the rotor shaft and the displacer elements (10, 12) are of a one-pieced design.
  6. The vacuum pump screw rotor according to any one of claims 1 to 5, characterized in that the at least one change of pitch between two adjacent displacer elements (10, 12) is non-uniform (abrupt).
  7. The vacuum pump screw rotor according to any one of claims 1 to 6, characterized in that the profile of the suction-side displacer element (10) is free of blowholes at least on one of the flanks.
  8. The vacuum pump screw rotor according to any one of claims 1 to 7, characterized in that, between two displacer elements (10, 12), a tool run-out zone is provided at the change of pitch, and/or that between two displacer elements (10, 12) a void is provided at the change of pitch in at least one of the flanks of the displacer elements (10, 12).
  9. The vacuum pump screw rotor according to any one of claims 1 to 8, characterized in that the entire vacuum pump screw rotor is made of aluminum or an aluminum alloy, particularly AlSi17Cu4Mg, wherein the aluminum has an expansion coefficient of less than 18*10-61/K, and that particularly a high silicon percentage of at least 15% is provided.
  10. A screw vacuum pump, comprising
    two mutually meshing screw rotors according to any one of claims 1 to 9,
    a housing (22) enclosing the screw rotors, and
    a drive means connected to the two screw rotors.
  11. The screw vacuum pump according to claim 10, characterized in that the internal compression of the screw vacuum pump is at least 2, particularly at least 4.
  12. The screw vacuum pump according to claim 10 or 11, characterized in that the screw rotors have a lower expansion coefficient than the housing (22), wherein the expansion coefficient of the housing (22) is particularly 5% and with particular preference 10% larger than that of the screw rotors, wherein the housing (22) is preferably made of aluminum or an aluminum alloy.
  13. The screw vacuum pump according to any one of claims 10 to 12, characterized in that, between the pressure-side displacer elements and the housing, a gap is arranged, said gap having a height in the range of 0.05 mm to 0.5 mm, preferably 0.1 to 0.3 mm.
  14. A method for producing a screw rotor according to any one of claims 1 to 9, comprising the steps of:
    - providing a base body of the screw rotor,
    - generating a helical recess of a first displacer element by use of a form cutter or a grinding screw, and
    - generating a further helical recess of a further displacer element by use of a further form cutter or grinding screw.
  15. The method according to claim 14, characterized in that the manufacturing of displacer elements with symmetric profile is performed by use of a single tool, particularly in one working step.
  16. The method according to claim 14 or 15, characterized in that, between adjacent displacer elements, prior to generating the helical recesses, a particularly circular cylindrical recess is generated as a tool run-out zone.
  17. The method according to any one of claims 14 to 16, characterized in that, between two adjacent displacer elements, a recess is generated in at least one flank for withdrawal of the tool.
  18. The method according to any one of claims 14 to 17, characterized in that, to generate the helical recesses, use is made, for each displacer element, of a tool reproducing the outer contour of the helical recess.
  19. The method according to any one of claims 14 to 18, characterized in that the base body is cylindrical, wherein the base body is preferably formed as a semi-finished product with already partially preformed recess and/or bearing pin.
EP17749704.7A 2016-08-30 2017-08-08 Vacuum pump screw rotor Active EP3507497B1 (en)

Applications Claiming Priority (2)

Application Number Priority Date Filing Date Title
DE102016216279.9A DE102016216279A1 (en) 2016-08-30 2016-08-30 Vacuum-screw rotor
PCT/EP2017/070065 WO2018041556A1 (en) 2016-08-30 2017-08-08 Vacuum pump screw rotor

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EP3507497A1 EP3507497A1 (en) 2019-07-10
EP3507497B1 true EP3507497B1 (en) 2024-04-17

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JP (1) JP6983872B2 (en)
KR (1) KR102390690B1 (en)
CN (1) CN109642575B (en)
BR (1) BR112019002011A2 (en)
CA (1) CA3032345A1 (en)
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BR112019002011A2 (en) 2019-05-14
US11293435B2 (en) 2022-04-05
DE102016216279A1 (en) 2018-03-01
WO2018041556A1 (en) 2018-03-08
CA3032345A1 (en) 2018-03-08
JP2019528400A (en) 2019-10-10
JP6983872B2 (en) 2021-12-17
EP3507497A1 (en) 2019-07-10
CN109642575B (en) 2021-02-26
KR102390690B1 (en) 2022-04-26
CN109642575A (en) 2019-04-16
US20190211822A1 (en) 2019-07-11

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