FR3116309A1 - Vacuum pump - Google Patents

Abstract

Dry vacuum pump (1) comprising:- a stator (2) having at least one compression chamber (3) in which the gases to be pumped are intended to circulate,- two rotors (4) configured to rotate in the at least one compression chamber (3) of the stator (2) to drive the gas to be pumped between a suction port (5) and a discharge port of the stator (2), characterized in that the vacuum pump (1) further comprises at least one magnet (9) arranged in at least one rotor (4) so as to face a surface (10, 12, 16) of ferromagnetic material of the stator (2) with each rotation of the at least one rotor (4) so that the rotation of the at least one rotor (4) causes the surface (10, 12, 16) of ferromagnetic material to be heated by magnetic induction. - Picture 2 -

Description

Vacuum pump

The present invention relates to a vacuum pump, such as a dry vacuum pump or a turbomolecular vacuum pump.

Dry or turbomolecular vacuum pumps can be used in processes using chemistries that generate sometimes solid reaction by-products. This is the case, for example, of certain manufacturing processes for semiconductors, photovoltaic screens, flat screens or LEDs. These solid by-products can be sucked up by the vacuum pump and alter its operation, in particular by interfering with the rotation of the rotor(s), or even preventing it completely in the worst case.

To avoid this, it is known to heat the stator of vacuum pumps using resistive blocks mounted in contact with the stator. The heating of the stator makes it possible to maintain the polluting gaseous species in gaseous form and thus to avoid their condensation or their solidification into powder or sludge inside the vacuum pump.

However, the heating temperature is limited, generally around 110°C in dry vacuum pumps or 120°C in turbomolecular vacuum pumps, because too high a temperature can risk damaging mechanical parts such as the bearings of the vacuum pump. dry vacuum or cause the turbomolecular vacuum pump rotor to creep.

This limited heating may not be sufficient to completely prevent deposits in the vacuum pump.

One of the aims of the present invention is to solve at least one of the drawbacks of the state of the art.

To this end, the subject of the invention is a dry vacuum pump comprising:
- a stator having at least one compression chamber in which the gases to be pumped are intended to circulate,
- two rotors configured to rotate in the at least one compression chamber of the stator to cause the gas to be pumped between a suction port and a discharge port of the stator,
characterized in that the vacuum pump further comprises at least one magnet arranged in at least one rotor so as to face a surface of ferromagnetic material of the stator on each rotation of the at least one rotor so that the rotation of the at least one rotor leads to heating of the ferromagnetic material surface by magnetic induction.

The rotational movement of the rotors is used to generate additional heating of the stator by magnetic induction. The rotational movement of the magnets generates eddy currents in the ferromagnetic material surface which in turn generate heat by the Joule effect. Eddy currents are electric currents created by the variation of the magnetic field generated by the rotation of magnets. This heating can make it possible to increase the temperature of the stator locally at the surface, for example from 5° C. to 30° C., which can make it possible to preserve the polluting gaseous species in gaseous form. The magnetic field making it possible to obtain this heating is for example between 0.3T and 1.5T. Localized heating is thus obtained at the level of the internal zones of the vacuum pump prone to deposits, on the surface, and without contact with the stator. The localized heating on the surface prevents damage to the mechanical parts which could not be heated in the mass beyond the temperature obtained with the conventional heating of the stator, such as the bearings, and makes it possible to limit the problems of thermal expansion of the stator.

The dry vacuum pump may further comprise one or more of the characteristics which are described below, taken alone or in combination.

At least one magnet extends for example axially in a rotor element of the rotor with a longitudinal direction parallel to the axis of rotation of the rotors, on a lateral end surface of the rotor element configured to sweep a lateral surface of the compression chamber.

At least one magnet extends for example in a rotor element of the rotor with a face perpendicular to the axis of rotation of the rotors, on a transverse end surface of the rotor element configured to sweep a transverse surface of the chamber of compression.

The transverse surface is for example that of the bottom of the compression chamber of the first or of the last pumping stage, the transverse surface being interposed between the compression chamber and a bearing support of the stator.

The dry vacuum pump comprises for example at least one magnet per rotor element of at least one compression chamber, at least one magnet arranged on a lateral end surface of the rotor element and/or at least one magnet arranged on a transverse end surface of the rotor element.

The dry vacuum pump may comprise at least two magnets per rotor element or per rotor, the polarity of the magnets being reversed in the thickness or in the length or at each adjacent magnet or at each adjacent rotor element.

The dry vacuum pump is for example a multistage primary vacuum pump. A primary vacuum pump is a volumetric vacuum pump, which is configured to, using the two rotors, suck, transfer and then deliver the gas to be pumped at atmospheric pressure. According to another example, the vacuum pump is of the Roots compressor type and comprises one to three pumping stages. Roots compressor type vacuum pumps are connected in series and upstream of a rough vacuum pump.

The dry vacuum pump, primary or Roots compressor, may comprise at least three pumping stages arranged in series, the at least one magnet being arranged in a rotor element configured to rotate in the last and/or penultimate pumping stage in the direction of gas flow.

At least one magnet may be arranged in a shaft of the rotor to heat a ferromagnetic material surface of a shaft passage of the stator.

The at least one magnet is for example of the NdFeB or rare earth type. According to another example, the at least one magnet comprises a ferrite. Ferrite is inexpensive but has the disadvantage of generating a weak magnetic field.

The at least one magnet can be coated with nickel to protect it from possible corrosive attacks or to allow its easy replacement by dismantling.

Preferably, the at least one magnet is arranged closest to the surface of the rotor or is flush with the surface of the rotor. The at least one magnet is for example fixed, for example by gluing to the body of the rotor, or is received in a cavity of the body of the rotor.

At least one surface layer of the stator having a surface of ferromagnetic material is for example made of an alloy of iron and nickel, also called "mu-metal", such as nickel-enriched cast iron, also called "Ni-resist". Indeed, the magnetic permeability of mu-metals is greater than that of cast iron. Mu-metals also have the advantage of allowing the generation of a significant Joule effect. The stator body can be made of a first material, such as cast iron and have a surface layer of ferromagnetic material or the stator can be made in the mass of ferromagnetic material, such as an alloy of iron and nickel.

At least one ferromagnetic material surface may include a nickel coating. The nickel coating provides greater surface heating. This heating increases with the thickness of the coating. For example, a coating is provided whose thickness is between 20 μm and 2 cm, in particular for rotors rotating between 60 and 250 Hz.

The invention also relates to a turbomolecular vacuum pump comprising:
- a stator having a compression chamber in which the gases to be pumped are intended to circulate,
- a rotor configured to rotate in the compression chamber of the stator to cause the gas to be pumped between a suction port and a discharge port of the stator,
characterized in that the vacuum pump further comprises at least one magnet arranged in the stator so as to face a surface of ferromagnetic material of the rotor on each rotation of the rotor so that the rotation of the rotor causes a heating of the surface in ferromagnetic material by magnetic induction.

The rotational movement of the rotor is used to generate additional heating of the rotor by magnetic induction. The rotational movement of the rotor facing the magnet(s) generates eddy currents in the ferromagnetic material surface which in turn generate heat by the Joule effect. Eddy currents are electrical currents created by the rotation of the rotor in the magnetic field of the stator magnets. This heating can make it possible to locally increase the surface temperature of the rotor, for example from 5°C to 30°C, which makes it possible to preserve the polluting gaseous species in gaseous form. The magnetic field making it possible to obtain this heating is for example between 0.3T and 1.5T. Localized heating is thus obtained at the level of the internal zones of the vacuum pump prone to deposits, on the surface, and without contact with the rotor. Localized and surface heating makes it possible not to damage the rotor by avoiding heating it entirely in the mass and makes it possible to limit the problems of thermal expansion of the stator.

The turbomolecular vacuum pump may further comprise one or more of the characteristics which are described below, taken alone or in combination.

The turbomolecular vacuum pump may comprise a plurality of magnets arranged in the stator in an area facing the ferromagnetic material surface of the rotor, the polarity of the adjacent magnets being reversed in the thickness or in the length or at each adjacent magnet .

The rotor may have a Holweck skirt bearing the surface of ferromagnetic material.

The at least one magnet is for example arranged in a molecular stage of the vacuum pump, in a zone of the stator surrounding the Holweck skirt or situated under the Holweck skirt.

As before, the at least one magnet is for example of the NdFeB or rare earth or ferrite type. It can be coated with nickel to protect it from possible corrosive attacks or to allow its easy replacement by dismantling. Preferably, the at least one magnet is arranged closest to the surface of the stator or is flush with the surface of the stator. The at least one magnet is for example fixed, for example by gluing to the stator, or is received in a cavity of the stator.

At least one part of the rotor having a surface made of ferromagnetic material is for example made of iron or of nickel or of cobalt.

The rotor can be made in a single piece of ferromagnetic material.

The invention also relates to a turbomolecular vacuum pump comprising:
- a stator having a compression chamber in which the gases to be pumped are intended to circulate,
- a rotor configured to rotate in the compression chamber of the stator to cause the gas to be pumped between a suction port and a discharge port of the stator,
characterized in that the vacuum pump further comprises a magnetic material arranged in the rotor so as to face a surface of ferromagnetic material of the stator on each rotation of the rotor so that the rotation of the rotor causes the surface of the material to heat up ferromagnetic by magnetic induction.

The magnetized material comprises, for example, fibers comprising cobalt or or nanowires comprising cobalt embedded in a composite.

The rotor has for example a Holweck skirt, the magnetic material being arranged in the Holweck skirt.

Furthermore, in all the previously described embodiments of dry or turbomolecular vacuum pumps, at least one surface of the rotor made of ferromagnetic material may comprise a nickel coating.

Presentation of drawings

Other characteristics and advantages of the invention will emerge from the following description, given by way of example, without limitation, with reference to the appended drawings in which:

There shows a schematic view of elements in perspective of a dry vacuum pump.

There shows a schematic sectional and side view of an example of the dry vacuum pump stator from the with a dotted rotor.

There shows a perspective view of an example of a rotor element of a rotor of the dry vacuum pump of the .

There shows a perspective view of another example of a rotor element of a rotor of the dry vacuum pump of the .

There shows a front and top view of another example of a rotor element of a rotor of the dry vacuum pump of the .

There shows a front and top view of another example of a rotor element of a rotor of the dry vacuum pump of the .

There shows a front and top view of another example of the rotor element of a rotor of the dry vacuum pump of the .

There shows a front and top view of another example of the rotor element of a rotor of the dry vacuum pump of the .

There is a schematic representation of a stator portion seen in section at the level of a surface made of ferromagnetic material.

There is a schematic representation of two rotors in a compression chamber of a dry vacuum pump according to an alternative embodiment.

There shows a schematic sectional view of a first embodiment for a turbomolecular vacuum pump.

There shows a schematic sectional view of a second embodiment for a turbomolecular vacuum pump.

In these figures, identical elements bear the same reference numbers. The following achievements are examples. Although the description refers to one or more embodiments, this does not necessarily mean that each reference is to the same embodiment, or that the features apply only to a single embodiment. Simple features of different embodiments can also be combined or interchanged to provide other embodiments.

The term “upstream” means an element which is placed before another with respect to the direction of circulation of the gases to be pumped. Conversely, the term "downstream" means an element placed after another with respect to the direction of flow of the gas to be pumped.

The axial direction is defined as the longitudinal direction of the vacuum pump in which the axis(es) of rotation of the rotor(s) extend.

Figures 1 and 2 illustrate a first example of vacuum pump 1.

Vacuum pump 1 is a dry vacuum pump.

The dry vacuum pump 1 comprises a stator 2 having at least one compression chamber 3 in which the gas to be pumped circulates and two rotors 4 configured to rotate in the at least one compression chamber 3 of the stator 2 to drive the gas to be pumped between a suction port 5 and a discharge port of the stator 2 (arrows G on the ).

In this first example, the rotors 4 are configured to rotate synchronously in the opposite direction in the at least one compression chamber 3 of the stator 2 to drive the gas to be pumped G. The rotors 4 have respective rotor elements 6, in particular at the least two rotor elements 6 per rotor 4 in each compression chamber 3. The rotor elements 6 are for example lobes of identical profiles, such as of the “Roots” type. Each rotor 4 comprises for example two rotor elements 6 per compression chamber 3, as in the diagrams (cross-section in the shape of an "eight" or "bean") or more (trilobes, tetralobes (see ) or pentalobes) or are of the "Claw" type or of another similar principle of positive-displacement vacuum pump.

The shafts 7 of the rotors 4 are driven by a motor of a motorization part of the vacuum pump 1 (not shown), located at one end of the vacuum pump 1, on the side of the discharge orifice or the suction port 5.

The dry vacuum pump 1 is for example a multistage primary vacuum pump. A primary vacuum pump is a volumetric vacuum pump, which is configured to, using the two rotors 4, suck, transfer and then deliver the gas to be pumped at atmospheric pressure. According to another example, the vacuum pump 1 is of the Roots compressor type and comprises one to three pumping stages. Roots compressor type vacuum pumps are connected in series and upstream of a rough vacuum pump.

In the illustrative example, the vacuum pump 1 comprises at least two pumping stages, such as between two and eight pumping stages, here five T1-T5. Each pumping stage T1-T5 of the stator 2 is formed by a compression chamber 3 receiving two mating rotors 4, the compression chambers 3 comprising a respective inlet and outlet. The successive pumping stages T1-T5 are connected in series one after the other by respective inter-stage channels 8 connecting the output (or the discharge) of the preceding pumping stage to the input (or the 'aspiration) of the stage which follows ( ). During rotation, the gas drawn in from the inlet is trapped in the volume generated by the rotors 4 and the stator 2, then is driven by the rotors 4 towards the following stage.

The inlet of the first pumping stage T1 communicates with the suction port 5 of the vacuum pump 1. The outlet of the last pumping stage T5 communicates with the discharge port. The axial dimensions of the rotor elements 6 and of the compression chambers 3 are for example equal or decreasing with the order of arrangement of the pumping stages T1-T5 in the gas pumping direction, the pumping stage T1 located on the side of the suction orifice 5 receiving the rotor elements 6 of larger axial dimension.

The vacuum pump 1 is in particular called "dry" because in operation, the rotors 4 turn inside the stator 2 without any mechanical contact between them or with the stator 2, which makes it possible not to use oil in the pumping stages T1-T5.

The vacuum pump 1 further comprises at least one magnet 9 arranged in at least one rotor 4 so as to face a surface 10, 12, 16 made of ferromagnetic material of the stator 2 on each rotation of the at least one rotor 4 so that the rotation of at least one rotor 4 causes heating of the surface 10, 12, 16 of ferromagnetic material by magnetic induction.

The rotational movement of the rotors 4 is used to generate additional heating of the stator 2 by magnetic induction. The rotational movement of the magnets 9 generate eddy currents in the surface 10, 12, 16 of ferromagnetic material which in turn generate heat by the Joule effect. Eddy currents are electric currents created by the variation of the magnetic field generated by the rotation of magnets. This heating can make it possible to locally increase the temperature of the stator 2 at the surface, for example from 5° C. to 30° C., which can make it possible to keep the polluting gaseous species in gaseous form. Localized heating is thus obtained at the level of the internal zones of the vacuum pump 1 favorable to deposits, on the surface, and without contact of the stator 2. The localized heating on the surface makes it possible not to damage the mechanical parts which could not be heated. in the mass beyond the temperature obtained with the conventional heating of the stator 2, like the bearings, and makes it possible to limit the problems of thermal expansion of the stator 2.

The at least one magnet 9 has for example the shape of a bar (elongated and parallelepipedic) or of a plate, for example less than three millimeters.

According to an embodiment, and as shown in Figures 3a, 3b, 3c and 3d, at least one magnet 9 extends axially in a rotor element 6 of the rotor 4, with a longitudinal direction parallel to the axis of rotation I of the rotors 4. The at least one magnet 9 extends over a lateral end surface 6a of the rotor element 6 configured to sweep (without contact) a lateral surface 10 of the compression chamber 3, in order to heat the side surface 10 of the compression chamber 3 of the stator 2.

In the illustrative example, the side surface of the compression chamber 3 is a cylindrical surface, the shape of the compression chamber 3 being part of two cylindrical cavities parallel and parallel to the axial direction, the cylindrical cavities overlapping transversely (figures 1 and 2). The at least one magnet 9 arranged on a side end surface 6a (on the "back" of the rotor element 6) thus allows "radial" heating of the compression chamber 3.

The vacuum pump 1 comprises for example at least one magnet 9 per rotor element 6 in at least one compression chamber 3. There is for example a single magnet 9 per lateral end surface 6a of rotor element 6 and this ci covers for example the side end surface 6a ( ) or there are several magnets 9 in this same surface 6a, for example two (FIGS. 3a, 3b, 3d).

According to another embodiment, and as shown in Figures 4a and 4b, at least one magnet 9 extends in a rotor element 6 of the rotor 4, with a main face perpendicular to the axis of rotation I of the rotors 4 ( Figures 4a, 4b), for example radially ( ). The at least one magnet 9 extends over a transverse end surface 6b of the rotor element 6 configured to sweep (without contact) a transverse surface 12 of the compression chamber 3, to heat the transverse surface 12 of the chamber compressor 3 of stator 2.

In the illustrative example, the transverse surface 12 of the compression chamber 3 is a flat surface, like that of the transverse end surface 6b, perpendicular to the axis of rotation I of the rotors 4. The at least one magnet 9 arranged on a transverse end surface 6b (on one face of the rotor element 6) thus allows "axial" heating of the compression chamber 3.

The vacuum pump 1 comprises for example at least one magnet 9 per rotor element 6 in at least one compression chamber 3. There is for example a single magnet 9 per transverse end surface 6b of rotor element 6 ( ) or there are several magnets 9 in this same surface 6b, for example two ( ).

There are for example one or more magnets 9 on the two transverse end surfaces 6b of each rotor element 6 ( ).

There is for example at least one magnet 9 in at least one transverse end surface 6b and at least one magnet 9 in a lateral end surface 6a.

The transverse surface 12 of the compression chamber 3 is for example that of the bottom of the compression chamber 3 of the first or last pumping stage T1 or T5, the transverse surface 12 being interposed between the compression chamber 3 and a support 13 of bearings 14 of the stator 2 ( ). It is thus possible to heat very locally the transverse surface 12 of the bottom of the compression chamber 3 of the last or first pumping stage T5 without risking damaging the bearings 14.

When the vacuum pump 1 comprises more than one magnet 9 per rotor 4, it is advantageous to reverse the polarity of the adjacent magnets 9 to optimize the generation of eddy currents. Polarity inversions can be made in the thickness ( ) or in the length, i.e. in the axial direction ( ) or transversely, i.e. perpendicular to the axial direction (FIGS. 3c, 3d, 4a and 4b) or to each adjacent magnet ( , 4b) or to each adjacent rotor element 6 as will be seen below.

More specifically, on the where the polarity inversions are made in the thickness, each rotor element 6 received in the same compression chamber 3 is provided with two magnets 9, a magnet 9 whose surface facing the surface 10 of ferromagnetic material is polarized "south" and another magnet 9 whose surface vis-à-vis the surface 10 of magnetic material is polarized "north".

In the case of the where the polarity inversions are carried out lengthwise, each rotor element 6 received in the same compression chamber 3 is provided with two magnets 9, a magnet 9 whose surface facing the surface 10 of ferromagnetic material is polarized "south" at a first axial end of the rotor element 6 and "north" at a second axial end, and another magnet 9 whose surface facing the surface 10 of ferromagnetic material is polarized "north at the first axial end of the rotor element 6 and "south" at the second axial end.

In the case of a multistage vacuum pump 1, the vacuum pump 1 comprising at least three pumping stages T1-T5, it is not possible to provide all the rotor elements 6 with magnets. These are, for example, the rotor elements 6 configured to rotate in the last and/or penultimate pumping stage T4, T5 in the direction of gas circulation, which are provided with magnets 9 ( ). Indeed, these are the pumping stages where the pressures, and therefore the risks of deposits, are the highest.

According to another exemplary embodiment also visible on the , at least one magnet 9 is arranged in the shaft 7 of the rotor 4, for example between two compression chambers 3 in the case of a multistage vacuum pump 1, to heat the surface 16 of a shaft passage of the stator 2.

The at least one magnet 9 is for example of the NdFeB or rare earth type. According to another example, the at least one magnet comprises a ferrite. Ferrite is inexpensive but has the disadvantage of generating a weak magnetic field.

The at least one magnet 9 can be coated with nickel to protect it from possible corrosive attacks or to allow its easy replacement by dismantling. Preferably, the at least one magnet 9 is arranged closest to the surface of the rotor 4 or is flush with the surface of the rotor 4. The at least one magnet 9 is for example fixed, for example by gluing to the body of the rotor 4, or is received in a cavity of the body of the rotor 4.

The body 2a of stator 2 is for example made of cast iron.

At least one surface layer 2b of the stator 2 having a surface 10 of ferromagnetic material is for example made of an alloy of iron and nickel, also called "mu-metal", such as nickel-enriched cast iron also called "Ni-resist » ( ). Indeed, the magnetic permeability of mu-metals is greater than that of cast iron. Mu-metals also have the advantage of allowing the generation of a significant Joule effect. The body 2a of stator 2 can be made of a first material, such as cast iron and have a surface layer 2b of ferromagnetic material or the stator 2 (body 2a and surface layer 2b) can be made in the mass of ferromagnetic material, such as an alloy of iron and nickel.

Furthermore, at least one surface 10 of ferromagnetic material of the stator 2 may include a coating 28 of nickel. The 28 nickel coating provides greater surface heating. This heating increases with the thickness of the coating 28. For example, a coating 28 is provided whose thickness is between 20 μm and 2 cm, in particular for rotors 4 rotating between 60 and 250 Hz.

Thus, according to an embodiment of the surface 10 in ferromagnetic material illustrated in the , the body 2a of the stator 2 is made of cast iron, a surface layer 2b of the stator 2 is made of an alloy of iron and nickel and has a coating 28 of nickel.

The stator 2 is for example composed of stator elements assembled together and only the stator element bearing the surface 10 of ferromagnetic material can have a surface layer 2b of mu-metal coated with nickel in order to limit the costs.

Although FIGS. 1 to 4b illustrate an example of a rotor 4 of the bilobe type, for which the rotor 4 comprises two rotor elements 6 offset by 180° per compression chamber 3, other embodiments are of course possible.

There shows another example for which the rotor 4 is of the tetralobe type, that is to say comprising four rotor elements 6 offset by 90° per compression chamber 3, and where each rotor element 6 is provided with a single magnet 9 Provision can be made, in order to optimize the generation of currents, for the polarity of the magnets 9 to be reversed at each adjacent rotor element 6 as represented on the in the case of rotors 4 having an even number of rotor elements 6.

There illustrates a second example of vacuum pump 100.

Vacuum pump 100 is a turbomolecular vacuum pump.

It comprises a stator 2 having a compression chamber 3 in which the gases to be pumped are intended to circulate and a rotor 4 configured to rotate in the compression chamber 3 of the stator 2 to drive the gas to be pumped between a suction orifice 5 and a discharge orifice 17 of the stator 2 (arrows G on the ).

According to an exemplary embodiment, the vacuum pump 100 comprises a turbomolecular stage 18 and a molecular stage 19 located downstream of the turbomolecular stage 18 in the gas flow direction. The pumped gases enter through the suction port 5, first cross the turbomolecular stage 18, then the molecular stage 19, then the discharge, to then be evacuated through the discharge port 17 of the vacuum pump 100. In operation, the discharge port 17 is connected to a primary vacuum pump.

In the turbomolecular stage 18, the rotor 4 comprises at least two stages of blades 20 and the stator 2 comprises at least one stage of fins 21. The stages of blades 20 and fins 21 follow one another axially along the axis of rotation I of the rotor 4 in the turbomolecular stage 18. The rotor 4 comprises for example more than four stages of blades 20, such as for example between four and eight stages of blades 20 (six in the example illustrated on the ).

Each stage of blades 20 of the rotor 4 comprises inclined blades which depart in a substantially radial direction from a hub of the rotor 4 fixed to a shaft 7 of the turbomolecular vacuum pump 100. The blades 20 are regularly distributed around the periphery of the hub.

Each stage of fins 21 of the stator 2 comprises a crown from which depart, in a substantially radial direction, inclined fins, regularly distributed over the inner periphery of the crown. The fins of a stage of fins 21 of the stator 2 engage between the blades of two successive stages of blades 20 of the rotor 4. The rotor blades 4 and the stator fins 2 are angled to guide the pumped gas molecules to the molecular stage 19.

According to an exemplary embodiment, the rotor 4 comprises a Holweck skirt 22 in the molecular stage 19, formed by a smooth cylinder, which rotates facing helical grooves of the stator 2. The helical grooves make it possible to compress and guide the gases pumped towards repression.

The rotor 4 is fixed to a shaft 7 configured to be driven in rotation at high speed in axial rotation in the stator 2, for example a rotation at more than twenty thousand revolutions per minute, by means of a motor 23 of the pump vacuum 100 turbomolecular. The motor 23 is for example arranged under a bell of the stator 2, itself arranged under the Holweck skirt 22 of the rotor 4. The rotor 4 is guided laterally and axially by bearings 24 magnetic or mechanical. The vacuum pump 100 may also have spare bearings 25.

The vacuum pump 100 further comprises at least one magnet 9 arranged in the stator 2 so as to face a surface 27 of ferromagnetic material of the rotor 4 at each rotation of the rotor 4 so that the rotation of the rotor 4 causes heating of the the surface 27 of ferromagnetic material by magnetic induction.

The rotational movement of rotor 4 is used to generate additional heating of rotor 4 by magnetic induction. The rotational movement of the rotor 4 facing the magnet(s) 9 generates eddy currents in the surface 27 of ferromagnetic material which in turn generate heat by the Joule effect. Eddy currents are electric currents created by the rotation of the rotor 4 in the magnetic field of the magnets 9 of the stator 2. This heating can make it possible to increase the temperature of the rotor 4 locally at the surface, for example from 5° C. to 30 °C, which makes it possible to keep the polluting gaseous species in gaseous form. Localized heating is thus obtained at the level of the internal zones of the vacuum pump 1 favorable to deposits, on the surface, and without contact with the rotor 4. The localized and surface heating makes it possible not to damage the rotor 4 by avoiding heating it. integrally in the mass and makes it possible to limit the problems of thermal expansion of the stator 2.

The at least one magnet 9 is for example arranged in the molecular stage 19 of the vacuum pump 100, in a zone of the stator 2 surrounding the rotor 4, such as for example surrounding the Holweck skirt 22 or as represented on the , located under the Holweck skirt 22. The surface 27 of ferromagnetic material is for example the Holweck skirt 22.

The vacuum pump 100 comprises for example a plurality of magnets 9, for example regularly distributed, the polarity of the adjacent magnets 9 being reversed in the thickness or in the length or between adjacent magnets.

As before, the at least one magnet 9 is for example of the NdFeB or rare earth or ferrite type. It can be coated with nickel to protect it from possible corrosive attacks or to allow its easy replacement by dismantling. Preferably, the at least one magnet 9 is arranged closest to the surface of the stator 2 or is flush with the surface of the stator 2. The at least one magnet 9 is for example fixed, for example by gluing to the stator 4, or is received in a cavity of the stator 4.

At least a part of the rotor 4 having a surface 27 of ferromagnetic material is for example made of iron or nickel or cobalt.

The rotor 4 can be made in a single piece of ferromagnetic material.

Furthermore, at least one surface 27 of ferromagnetic material of the rotor 4 may include a coating 28 of nickel.

There illustrates another example of a turbomolecular vacuum pump 200.

This vacuum pump 200 differs from the previous one in that here, a magnetic material 29 is arranged in the rotor 4 so as to face a surface 27 of ferromagnetic material of the stator 2 at each rotation of the rotor 4 so that the Rotation of the rotor 4 causes heating of the surface 27 of ferromagnetic material by magnetic induction.

The magnetic material 29 is for example arranged in the Holweck skirt 22 of the rotor 4. The surface 27 of ferromagnetic material is the surface of the stator 2 opposite the Holweck skirt 22.

For this, for example, the magnetized material comprises fibers or nanowires comprising cobalt, such as cobalt or such as AlNiCo, embedded in a composite. It is thus possible to reach fields of 0.6T for the speeds of rotation of the rotor 4 in the turbomolecular vacuum pump 200 .

The cobalt nanowires can be obtained in a polyol medium, for example by conventional thermal means or by microwaves. The alignment of the cobalt nanowires is obtained by drying under a very high magnetic field (a few T).

The nanowires or fibers comprising cobalt can be embedded in a polymer composite, such as PI (polyimide) or PPS (Polyphenylene sulphide) or PEI (polyetherimide) or PEEK (polyetheretherketone). Additives such as glass fibers can be incorporated into the composite to improve mechanical strength.

The initial orientation of the fibers or nanowires gives the polarity. The polarity is for example regularly reversed to obtain the alternation of the north and south magnetic fields on the periphery of the Holweck 22 skirt.

The rotor 4 can be made in one piece and only the Holweck skirt 22 is for example magnetized. Furthermore, at least one surface 27 of ferromagnetic material of the rotor 4 may include a coating 28 of nickel.

At least a part of the stator 2 having a surface 27 of ferromagnetic material is for example made of iron or nickel or cobalt.

Claims (20)

Dry vacuum pump (1) comprising:
- a stator (2) having at least one compression chamber (3) in which the gases to be pumped are intended to circulate,
- two rotors (4) configured to rotate in the at least one compression chamber (3) of the stator (2) to drive the gas to be pumped between a suction port (5) and a discharge port of the stator (2) ,
characterized in that the vacuum pump (1) further comprises at least one magnet (9) arranged in at least one rotor (4) so as to face a surface (10, 12, 16) of ferromagnetic material of the stator (2) each rotation of the at least one rotor (4) so that the rotation of the at least one rotor (4) causes the surface (10, 12, 16) of ferromagnetic material to be heated by magnetic induction. Vacuum pump (1) according to Claim 1, characterized in that at least one magnet (9) extends axially in a rotor element (6) of the rotor (4) with a longitudinal direction parallel to the axis of rotation (I) rotors (4), on a lateral end surface (6b) of the rotor element (6) configured to sweep a lateral surface (10) of the compression chamber (3). Vacuum pump (1) according to one of the preceding claims, characterized in that at least one magnet (9) extends in a rotor element (6) of the rotor (4) with a face perpendicular to the axis of rotation (I) of the rotors (4), on a transverse end surface (6b) of the rotor element (6) configured to sweep a transverse surface (12) of the compression chamber (3). Vacuum pump (1) according to the preceding claim, characterized in that the transverse surface (12) is that of the bottom of the compression chamber (3) of the first or last pumping stage (T1, T5), the surface ( 12) transverse being interposed between the compression chamber (3) and a support (13) of bearings (14) of the stator (2). Vacuum pump (1) according to one of Claims 3 or 4, taken together with Claim 2, characterized in that it comprises at least one magnet (9) per rotor element (6) of at least one compression chamber (3), at least one magnet (9) being arranged in a lateral end surface (6a) of the rotor element (6) and/or at least one magnet (9) being arranged in a transverse end surface (6b) of the rotor element (6). Vacuum pump (1; 100) according to one of the preceding claims, characterized in that it comprises at least two magnets (9) per rotor element (6) or per rotor (4), the polarity of the magnets (9) adjacent magnets being reversed in thickness or in length or to each adjacent magnet (9) or to each adjacent rotor element (6). Vacuum pump (1) according to one of the preceding claims, characterized in that the vacuum pump (1) comprises at least three pumping stages (T1-T5) arranged in series, the at least one magnet (9) being arranged in a rotor element (6) configured to rotate in the last and/or penultimate pumping stage (T4, T5) in the direction of gas circulation. Vacuum pump (1) according to one of the preceding claims, characterized in that at least one magnet (9) is arranged in a shaft (7) of the rotor (4) to heat a surface (16) of ferromagnetic material d stator shaft passage (2). Vacuum pump (1) according to one of the preceding claims, characterized in that at least one surface layer (2b) of the stator (2) having a surface (10, 12, 16) of ferromagnetic material is made of an alloy of iron and nickel. Vacuum pump (1) according to one of the preceding claims, characterized in that the stator (2) is made in the mass of a ferromagnetic material, such as an alloy of iron and nickel. Turbomolecular vacuum pump (100) comprising:
- a stator (2) having a compression chamber (3) in which the gases to be pumped are intended to circulate,
- a rotor (4) configured to rotate in the compression chamber (3) of the stator (2) to drive the gas to be pumped between a suction port (5) and a discharge port of the stator (2),
characterized in that the vacuum pump (100) further comprises at least one magnet (9) arranged in the stator (2) so as to face a surface (27) of ferromagnetic material of the rotor (4) at each rotation of the rotor (4) so that the rotation of the rotor (4) causes heating of the surface (27) of ferromagnetic material by magnetic induction. Vacuum pump (100) according to the preceding claim, characterized in that it comprises a plurality of magnets (9) arranged in the stator (2) in a zone located opposite the surface (27) of ferromagnetic material of the rotor ( 4), the polarity of the adjacent magnets (9) being reversed in the thickness or in the length or at each adjacent magnet. Vacuum pump (100) according to one of Claims 11 or 12, characterized in that the rotor (4) has a Holweck skirt (22) carrying the surface (27) of ferromagnetic material. Vacuum pump (100) according to the preceding claim, characterized in that the at least one magnet (9) is arranged in a molecular stage (19) of the vacuum pump (100), in a zone of the stator (2) surrounding the Holweck skirt (22) or located under the Holweck skirt (22). Vacuum pump (100) according to one of Claims 11 to 14, characterized in that at least part of the rotor (4) having a surface (27) of ferromagnetic material is made of iron or nickel or cobalt. Vacuum pump (1; 100) according to one of the preceding claims, characterized in that the at least one magnet (9) is coated with nickel. Turbomolecular vacuum pump (200) comprising:
- a stator (2) having a compression chamber (3) in which the gases to be pumped are intended to circulate,
- a rotor (4) configured to rotate in the compression chamber (3) of the stator (2) to drive the gas to be pumped between a suction port (5) and a discharge port of the stator (2),
characterized in that the vacuum pump (200) further comprises a magnetic material (29) arranged in the rotor (4) so as to face a surface (27) of ferromagnetic material of the stator (2) at each rotation of the rotor (4) so that the rotation of the rotor (4) causes heating of the surface (27) of ferromagnetic material by magnetic induction. Vacuum pump (200) according to the preceding claim, characterized in that the magnetized material comprises fibers or nanowires comprising cobalt embedded in a composite. Vacuum pump (200) according to one of Claims 17 or 18, characterized in that the rotor (4) has a Holweck skirt (22), the magnetic material (29) being arranged in the Holweck skirt (22). Vacuum pump (1; 100; 200) according to one of the preceding claims, characterized in that at least one surface (10, 12, 16, 27) of ferromagnetic material has a coating (28) of nickel.