EP1619395B1 - Rotary vacuum pump, structure and method for the balancing thereof - Google Patents
Rotary vacuum pump, structure and method for the balancing thereof Download PDFInfo
- Publication number
- EP1619395B1 EP1619395B1 EP04103445A EP04103445A EP1619395B1 EP 1619395 B1 EP1619395 B1 EP 1619395B1 EP 04103445 A EP04103445 A EP 04103445A EP 04103445 A EP04103445 A EP 04103445A EP 1619395 B1 EP1619395 B1 EP 1619395B1
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- EP
- European Patent Office
- Prior art keywords
- pump
- rotor
- rotating
- rotating shaft
- sensors
- 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.)
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Classifications
-
- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D19/00—Axial-flow pumps
- F04D19/02—Multi-stage pumps
- F04D19/04—Multi-stage pumps specially adapted to the production of a high vacuum, e.g. molecular pumps
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D17/00—Radial-flow pumps, e.g. centrifugal pumps; Helico-centrifugal pumps
- F04D17/08—Centrifugal pumps
- F04D17/16—Centrifugal pumps for displacing without appreciable compression
- F04D17/168—Pumps specially adapted to produce a vacuum
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D27/00—Control, e.g. regulation, of pumps, pumping installations or pumping systems specially adapted for elastic fluids
- F04D27/001—Testing thereof; Determination or simulation of flow characteristics; Stall or surge detection, e.g. condition monitoring
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- F—MECHANICAL ENGINEERING; LIGHTING; HEATING; WEAPONS; BLASTING
- F04—POSITIVE - DISPLACEMENT MACHINES FOR LIQUIDS; PUMPS FOR LIQUIDS OR ELASTIC FLUIDS
- F04D—NON-POSITIVE-DISPLACEMENT PUMPS
- F04D29/00—Details, component parts, or accessories
- F04D29/66—Combating cavitation, whirls, noise, vibration or the like; Balancing
- F04D29/661—Combating cavitation, whirls, noise, vibration or the like; Balancing especially adapted for elastic fluid pumps
- F04D29/662—Balancing of rotors
Definitions
- the present invention concerns a rotary vacuum pump and a structure and a method for the balancing thereof.
- the present invention concerns a rotary vacuum pump of the kind equipped with mechanical bearings.
- rotary pumps and especially turbomolecular rotary pumps, are machines equipped with a rotating portion, including a rotating shaft to which a set of parallel rotor discs are secured, and co-operating with a stationary portion, generally a set of stator discs, in order to obtain gas pumping from an inlet port to an outlet port of the pump.
- a turbomolecular pump can generate a vacuum of the order of 10 -7 mbar (10 -5 Pa) with a shaft rotation speed in the range 2x10 4 to 9x10 4 rpm.
- vibrations are sources of disturbances altering the operation of the measuring instrument and therefore they cannot be tolerated.
- balancing of a rotating mass can be obtained by means of further additional rotating masses, coupled to the main mass so that the centre of gravity of the overall mass is brought again on the rotation axis (static balancing) and the rotation axis coincides with a main axis of inertia (dynamic balancing).
- static balancing static balancing
- dynamic balancing dynamic balancing
- the pump rotor is dynamically balanced through an iterative process in which measuring steps of the vibrations transmitted by the pump to an external structure alternate with adjusting steps of the position of one or more additional masses placed on the rotor, until the optimum conditions are attained.
- the main problems related to the rotor balancing step are, on the one hand, the definition of the mathematical model used in order to relate the vibrations measured during the balancing step to the rotor unbalance and, consequently, to the arrangement of the correcting masses, and, on the other hand, the choice of the kind of vibration sensors and the arrangement thereof.
- the sensors generally used during the rotor balancing step are accelerometers, that is sensors capable of transforming the acceleration of a moving body to which they are secured into an electric signal, the intensity of which is just a function of the acceleration the sensor is being submitted to.
- the dynamic balancing of a vacuum pump rotor is performed by placing the pump, without stator discs, inside a bell-shaped casing onto which at least two accelerometers, for instance piezoelectric accelerometers, are located. Once the rotor is rotated at high speed, the accelerometers located onto the stationary bell allow measuring the vibrations induced by unbalances, if any, of the rotating masses.
- the iterative balancing process may need several pump stopping and starting phases in order to apply the correcting masses, and this results in a considerable increase of the time required to reach the optimum conditions and hence in a considerable slowing down of the production.
- EP 1,273,803 relates to a vacuum pump which includes a rotor and a body connected to said rotor through a connecting portion, so that the rotor and the body as a whole are balanced.
- the connecting portion is weaker than the rotor with respect to corrosive gasses, so that said connecting portion is damaged by corrosion before any corrosive gas influence appears in the rotor.
- the connecting portion breaks and the aforesaid body falls off, causing an unbalanced state to appear in the rotor.
- EP 1,273,803 discloses how to detect a corrosion risk and to prevent a corrosion damage starting from a balanced structure and using the unbalanced status caused by the falling of said body as a corrosion detector.
- the vibration measurement is not affected by the presence of other pump components, which allows a considerable simplification of the mathematical model relating the measured displacements to the rotor unbalance inducing them.
- the provision of displacement sensors permanently located inside the pump allows measuring the rotating mass unbalance also during steady state operation of the same pump, that is when the pump has been completed with the stator part, assembled and delivered to the customer.
- a first turbomolecular rotary pump 101 according to the invention is schematically shown.
- Said pump 101 comprises a stationary portion and a rotating portion.
- the stationary portion comprises a basement 103 on which the rotating portion is mounted.
- the latter comprises a rotating shaft 105 supported by rolling bearings 107, for instance ball bearings.
- Rotor 109 of electric motor 111 (the stator of which has not been shown for sake of simplicity) used to rotate shaft 105, and pump rotor 113, equipped with smooth or finned discs 115, are mounted on said rotating shaft 105.
- said pump rotor 113 has a bell-shaped cavity 117 housing rotating shaft 105 of the pump and electric motor 111, in order to make the pump axially more compact.
- Such an arrangement is generally used for big turbomolecular pumps (rotor diameter of about 250 mm).
- rotor 113 is not located inside the pump housing, which, as known, is equipped with stator discs, but inside a vacuum-tight stationary bell 119 specifically intended for the balancing of said rotor 113. Vacuum in said bell is made by means of an ancillary pumping system, not shown.
- a plurality of displacement sensors (four in the disclosed embodiment) 121A - 121D are directly mounted in basement 103 of pump 101, close to rotor 113 and to rotating shaft 105 thereof.
- Each sensor faces said shaft 105 or said rotor 113 so that changes, if any, in the distance between the rotor and the sensor during rotation of the rotor can be detected.
- a first pair of sensors 121A, 121B face rotating shaft 105 and are turned towards it, whereas a second pair of sensors 121C, 121D face inner wall 113a of rotor 113 and are turned towards such wall.
- eddy current displacement sensors are advantageously employed.
- a generic displacement sensor 51 comprising a coil 53, which is wound on a core 55 and in which a high frequency AC current generating a main magnetic field flows.
- the variation of distance "a" between coil 53 and an electrically conducting body R, for instance the pump rotor or the shaft thereof, causes a corresponding variation of the magnetic field induced and consequently of impedance Z measured in the coil of sensor 51.
- a voltage signal U the value of which depends on impedance Z and hence on the distance of the metal body from the sensor, can be obtained at the output from sensor 51.
- the circuit shown in Fig. 2 comprises a high frequency oscillator 65, an impedance 67 in series and a demodulator 63.
- Impedance 67 must be sufficiently high to obtain a high sensitivity.
- Demodulation of voltage signal u outgoing from the sensor allows obtaining a voltage signal U that is a function of distance "a".
- Eddy current displacement sensors are capable of measuring distance variations of the order of 1 nm and are perfectly suitable for use in balancing turbomolecular pump rotors.
- cylindrical threaded bores 123 are provided in rotor 113 and are arranged with their axes lying in a plane orthogonal to the rotation axis of the rotor and tangentially relative to the same rotor. Additional masses consisting of threaded dowels can be located and displaced in said bores.
- balancing methods comprise the insertion of masses consisting of threaded dowels to be screwed into bores with axes radially arranged relative to the rotor.
- FIG. 3b a second embodiment of the invention is partly depicted.
- a turbomolecular pump 201 differs from that previously disclosed with reference to Fig. 3a in that rotor 213 has no bell-shaped cavity receiving rotating shaft 205 and electric motor 211.
- Shaft 205 is instead supported by a pair of rolling bearings 207, for instance ball bearings, and is driven by an electric motor 211, the bearings and the motor being located in a pump region that is axially separated from the pumping region where rotor 213 is located.
- That arrangement is generally used for small and medium size turbomolecular pumps (rotor diameter smaller than about 160 mm).
- a pair of displacement sensors 221A, 221B is provided in basement 203 of pump 201, opposite rotating shaft 205 and at opposite sides of rotor 209 of electric motor 211.
- a second pair of sensors 221C, 221D is provided close to inner wall 213a of rotor 213, whereas a third pair of sensors 221E, 221F is provided close to outer wall 213b of rotor 213. Said sensors are turned towards said rotor so that any variation in the distance between the rotor and the sensor during rotation of the same rotor can be detected.
- bell 219 is advantageously equipped with a central cylindrical projection 219a penetrating into central bore 213c of rotor 213.
- a removable vertical support 220 is provided adjacent to one of the walls of external bell 219 for the cantilevering of the third pair of displacement sensors 221E, 221F.
- pump 201 has multiple threaded bores 223 with axes lying in planes orthogonal to the rotation axis of rotor 223 to allow locating and displacing additional masses.
- threaded dowels located in radial bores instead of tangentially oriented bores can be used.
Description
- The present invention concerns a rotary vacuum pump and a structure and a method for the balancing thereof.
- In the field of rotary vacuum pumps, it is known that either mechanical bearings, such as ball or roller bearings, or magnetic bearings can be used for supporting the rotating pump shaft.
- The present invention concerns a rotary vacuum pump of the kind equipped with mechanical bearings.
- More particularly, the present invention concerns a turbomolecular rotary vacuum pump of the kind disclosed for instance in
EP-A-0962264 orEP-A-0773367 . - As known, rotary pumps, and especially turbomolecular rotary pumps, are machines equipped with a rotating portion, including a rotating shaft to which a set of parallel rotor discs are secured, and co-operating with a stationary portion, generally a set of stator discs, in order to obtain gas pumping from an inlet port to an outlet port of the pump.
- Depending on the kind of pump, higher or lower vacuum degrees can be obtained. For instance, a turbomolecular pump can generate a vacuum of the order of 10-7 mbar (10-5 Pa) with a shaft rotation speed in the range 2x104 to 9x104 rpm.
- A vacuum pump is thus a machine with a mass that is rotated at extremely high speed. In a vacuum pump, such a rotating mass generally includes a rotating shaft, the rotor of the electric motor driving said shaft into rotation, the set of rotor discs and the inner rings of the rolling bearings rotatably supporting the pump shaft.
- When the rotating mass is not arranged with its centre of gravity on the rotation axis and thus is not balanced, forces of inertia are generated within the pump and are transmitted through the housing to the outside of the pump. Such forces of inertia cause unwanted stresses and vibrations, which are sources of noise and lead to an early wear of the rolling bearings.
- Moreover, in some specific applications, for instance where the pump is connected to a precision measuring instrument, such as in mass spectrometry, vibrations are sources of disturbances altering the operation of the measuring instrument and therefore they cannot be tolerated.
- One of the problems encountered in designing a rotary vacuum pump equipped with mechanical bearings is thus how to reduce the vibrations produced by the pump due to unbalance of the rotating masses.
- Generally, it is known that balancing of a rotating mass can be obtained by means of further additional rotating masses, coupled to the main mass so that the centre of gravity of the overall mass is brought again on the rotation axis (static balancing) and the rotation axis coincides with a main axis of inertia (dynamic balancing). A dynamically balanced rotor does not transmit stresses to the supports and it is therefore an optimum solution.
- In the field of rotary vacuum pumps, and in particular of turbomolecular ones, the pump rotor is dynamically balanced through an iterative process in which measuring steps of the vibrations transmitted by the pump to an external structure alternate with adjusting steps of the position of one or more additional masses placed on the rotor, until the optimum conditions are attained.
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DE 19627921 discloses a balancing technique for pump rotors. - The main problems related to the rotor balancing step are, on the one hand, the definition of the mathematical model used in order to relate the vibrations measured during the balancing step to the rotor unbalance and, consequently, to the arrangement of the correcting masses, and, on the other hand, the choice of the kind of vibration sensors and the arrangement thereof.
- In the field of rotary vacuum pumps, the sensors generally used during the rotor balancing step are accelerometers, that is sensors capable of transforming the acceleration of a moving body to which they are secured into an electric signal, the intensity of which is just a function of the acceleration the sensor is being submitted to.
- According to the prior art, the dynamic balancing of a vacuum pump rotor is performed by placing the pump, without stator discs, inside a bell-shaped casing onto which at least two accelerometers, for instance piezoelectric accelerometers, are located. Once the rotor is rotated at high speed, the accelerometers located onto the stationary bell allow measuring the vibrations induced by unbalances, if any, of the rotating masses.
- Yet such a solution has some drawbacks, of which the main is that the point where vibrations are measured, i.e. the area where the accelerometer is located, is relatively far from the source of said vibrations, i.e. the rotor.
- The provision of a set of masses placed between the rotor and the accelerometer, and comprising members that in part are very rigid and in part are resilient and damping, makes it complex to define a reliable mathematical model relating the vibrations to their cause, i.e. the unbalance of the rotor and the other moving masses.
- Consequently, the iterative balancing process may need several pump stopping and starting phases in order to apply the correcting masses, and this results in a considerable increase of the time required to reach the optimum conditions and hence in a considerable slowing down of the production.
-
EP 1,273,803 relates to a vacuum pump which includes a rotor and a body connected to said rotor through a connecting portion, so that the rotor and the body as a whole are balanced. The connecting portion is weaker than the rotor with respect to corrosive gasses, so that said connecting portion is damaged by corrosion before any corrosive gas influence appears in the rotor. As a consequence, in corrosive atmospheres, before than the rotor is damaged, the connecting portion breaks and the aforesaid body falls off, causing an unbalanced state to appear in the rotor. - Thus,
EP 1,273,803 discloses how to detect a corrosion risk and to prevent a corrosion damage starting from a balanced structure and using the unbalanced status caused by the falling of said body as a corrosion detector. - It is the main object of the present invention to solve the problem of how effectively and quickly to balance the rotating masses of a rotary vacuum pump, more particularly a pump equipped with mechanical bearings such as a turbomolecular vacuum pump.
- The above and other objects are achieved by means of a vacuum pump and a balancing method as claimed in the appended claims.
- Thanks to the positioning of displacement sensors close to the rotating masses of the pump, it is possible to obtain a more direct measurement of the rotor vibrations and hence to make the proper balancing thereof simpler and quicker.
- According to the invention, the vibration measurement is not affected by the presence of other pump components, which allows a considerable simplification of the mathematical model relating the measured displacements to the rotor unbalance inducing them.
- Advantageously, the provision of displacement sensors permanently located inside the pump allows measuring the rotating mass unbalance also during steady state operation of the same pump, that is when the pump has been completed with the stator part, assembled and delivered to the customer.
- Two embodiments of the invention, given by way of non-limiting example, will be described hereinbelow with reference to the accompanying drawings, in which:
-
Fig. 1 is a diagrammatic view of the displacement sensor; -
Fig. 2 is a diagram of the electronic circuitry of the displacement sensor; -
Fig. 3a is a cross-sectional view of a first example of a vacuum pump according to the invention; -
Fig. 3b is a cross-sectional view of a second example of a vacuum pump according to the invention. - Referring to
Fig. 3a , a firstturbomolecular rotary pump 101 according to the invention is schematically shown. - Said
pump 101 comprises a stationary portion and a rotating portion. The stationary portion comprises abasement 103 on which the rotating portion is mounted. The latter comprises a rotatingshaft 105 supported byrolling bearings 107, for instance ball bearings.Rotor 109 of electric motor 111 (the stator of which has not been shown for sake of simplicity) used to rotateshaft 105, andpump rotor 113, equipped with smooth orfinned discs 115, are mounted on said rotatingshaft 105. - As clearly shown in
Fig. 3a , according to the construction design ofpump 101, saidpump rotor 113 has a bell-shapedcavity 117housing rotating shaft 105 of the pump andelectric motor 111, in order to make the pump axially more compact. Such an arrangement is generally used for big turbomolecular pumps (rotor diameter of about 250 mm). - In
fig. 3a the pump is shown during the balancing phase and hencerotor 113 is not located inside the pump housing, which, as known, is equipped with stator discs, but inside a vacuum-tightstationary bell 119 specifically intended for the balancing of saidrotor 113. Vacuum in said bell is made by means of an ancillary pumping system, not shown. - According to the invention, a plurality of displacement sensors (four in the disclosed embodiment) 121A - 121D are directly mounted in
basement 103 ofpump 101, close torotor 113 and to rotatingshaft 105 thereof. Each sensor faces saidshaft 105 or saidrotor 113 so that changes, if any, in the distance between the rotor and the sensor during rotation of the rotor can be detected. - More particularly, in the case depicted in
Fig. 3a , a first pair ofsensors shaft 105 and are turned towards it, whereas a second pair ofsensors inner wall 113a ofrotor 113 and are turned towards such wall. - According to the invention, eddy current displacement sensors are advantageously employed.
- Referring to
Fig. 1 , there is schematically shown ageneric displacement sensor 51 comprising acoil 53, which is wound on acore 55 and in which a high frequency AC current generating a main magnetic field flows. The variation of distance "a" betweencoil 53 and an electrically conducting body R, for instance the pump rotor or the shaft thereof, causes a corresponding variation of the magnetic field induced and consequently of impedance Z measured in the coil ofsensor 51. - By using an impedance-to-voltage converter, such as that shown in
Fig. 2 , a voltage signal U, the value of which depends on impedance Z and hence on the distance of the metal body from the sensor, can be obtained at the output fromsensor 51. - More precisely, the circuit shown in
Fig. 2 comprises ahigh frequency oscillator 65, animpedance 67 in series and ademodulator 63.Impedance 67 must be sufficiently high to obtain a high sensitivity. Demodulation of voltage signal u outgoing from the sensor allows obtaining a voltage signal U that is a function of distance "a". - Eddy current displacement sensors are capable of measuring distance variations of the order of 1 nm and are perfectly suitable for use in balancing turbomolecular pump rotors.
- More particularly, in the described case, a variation of the distance of
internal wall 113a ofrotor 113 from facingsensors rotor 113, will cause a measurable impedance variation in said sensors. By measuring such an impedance variation, it is possible to obtain the distance variation, and hence the unbalance having generated it, and to correct such unbalance. - The process in case of a distance variation between
rotating shaft 105 andsensors - To correct the unbalance of
rotor 113, cylindrical threadedbores 123 are provided inrotor 113 and are arranged with their axes lying in a plane orthogonal to the rotation axis of the rotor and tangentially relative to the same rotor. Additional masses consisting of threaded dowels can be located and displaced in said bores. - As an alternative, other balancing methods comprise the insertion of masses consisting of threaded dowels to be screwed into bores with axes radially arranged relative to the rotor.
- Further in accordance with the invention, and still referring to
Fig. 3a , a third pair ofdisplacement sensors external wall 113b ofrotor 113, between a pair of said rotor discs, and are turned towards said wall. Saidsensors vertical support 120 adjacent to a wall ofouter bell 119. - It is clear that, at the end of the balancing phase,
bell 119 andsupport 120, if provided, will be removed and replaced by pump housing 121 with the stator integral thereto, so that the pump will be ready for being sent to the customer and used. Consequently, at the end of the balancing phase,displacement sensors bell 119 will be removed. On the contrary,sensors 121A - 121D mounted inbasement 103 ofpump 101 will remain inside said pump even during operation thereof, and they could be advantageously used to carry out measurements on the rotor balance conditions during normal pump operation. - Turning now to
Fig. 3b , a second embodiment of the invention is partly depicted. - A
turbomolecular pump 201 differs from that previously disclosed with reference toFig. 3a in thatrotor 213 has no bell-shaped cavity receivingrotating shaft 205 andelectric motor 211.Shaft 205 is instead supported by a pair of rollingbearings 207, for instance ball bearings, and is driven by anelectric motor 211, the bearings and the motor being located in a pump region that is axially separated from the pumping region whererotor 213 is located. - That arrangement is generally used for small and medium size turbomolecular pumps (rotor diameter smaller than about 160 mm).
- Similarly to what described above, according to the invention a pair of
displacement sensors basement 203 ofpump 201, opposite rotatingshaft 205 and at opposite sides ofrotor 209 ofelectric motor 211. - Also in that second example, said displacement sensors are preferably eddy current sensors.
- Like in the previous embodiment,
further displacement sensors face rotor 213. - More particularly, in the embodiment shown, a second pair of
sensors 221C, 221D is provided close toinner wall 213a ofrotor 213, whereas a third pair ofsensors outer wall 213b ofrotor 213. Said sensors are turned towards said rotor so that any variation in the distance between the rotor and the sensor during rotation of the same rotor can be detected. - In order to properly locate the second pair of
sensors 221C, 221D, bell 219 is advantageously equipped with a central cylindrical projection 219a penetrating into central bore 213c ofrotor 213. - A removable
vertical support 220 is provided adjacent to one of the walls of external bell 219 for the cantilevering of the third pair ofdisplacement sensors - Like in the previously disclosed pump, also pump 201 has multiple threaded
bores 223 with axes lying in planes orthogonal to the rotation axis ofrotor 223 to allow locating and displacing additional masses. - Also in this case, threaded dowels located in radial bores instead of tangentially oriented bores can be used.
- When, at the end of the balancing phase, bell 219 and
support 220, if present, will be removed,displacement sensors sensors basement 203 ofpump 201 will remain inside said pump even during operation thereof, and they could be advantageously used to carry out field measurements. - It is clear that the turbomolecular pump according to the invention attains the intended aims, since using displacement sensors directly mounted inside the pump, close to the rotor or the rotating shaft thereof, allows using simpler and more precise mathematical models to determine the rotor unbalance. Consequently, the balancing phase might be carried out in quicker manner and with better results.
- It is also clear that the above description has been given only by way of non-limiting example and that several modifications are possible without departing from the scope of the invention, as defined in the appended claims.
Claims (15)
- A rotary vacuum pump (101; 201) comprising a stationary portion (103; 203) and a portion rotating relative to said stationary portion, said rotating portion comprising a rotating shaft (105; 205) equipped with a rotor assembly (113; 213) co-operating with a stator assembly for gas pumping, said rotating shaft being driven by an electric motor (111; 211) and being supported by at least one rolling mechanical bearing (107; 207) relative to said stationary portion, characterised in that at least two displacement sensors (121A-121D; 221A-221B), capable of generating an electrical signal varying with the distance between said stationary portion and said rotating portion during the rotation of said shaft and said rotor assembly, are provided between said stationary portion and said rotating portion.
- A pump as claimed in claim 1, wherein said pump (101) comprises a basement (103) on which the rotating shaft (105) supported by a pair of rolling bearings (107) is mounted, the rotor (109) of the pump electric motor (111) used to rotate the shaft (105) and the pump rotor (113) being mounted on said rotating shaft (105).
- The pump as claimed in claim 2, wherein said pump rotor (113) has a bell-shaped cavity (117) housing the pump rotating shaft (105) and the electric motor (111).
- The pump as claimed in claim 3, wherein said pump comprises at least one pair of displacement sensors (121A- 121D) mounted in the basement (103) of the pump (101), close to the rotor (113) and/or to the rotating shaft (105) thereof, each sensor facing said shaft (105) or said rotor (113) so that the variation, if any, in the distance between the rotor and the sensor during rotation of the rotor can be measured.
- The pump as claimed in claim 4, wherein said pump comprises a first pair of sensors (121A, 121B) facing the rotating shaft (105) and turned towards it, and a second pair of sensors (121C, 121D) facing the inner wall (113a) of the rotor (113) and turned towards such wall.
- The pump as claimed in claim 1, wherein said rotor (113) comprises at least one threaded cylindrical bore (123) arranged with its axis lying in a plane orthogonal to the rotation axis of the rotor (113) and tangentially relative to said rotor, in which bore additional masses consisting of threaded dowels can be located and displaced in order to reduce the unbalance of said rotating portion.
- The pump as claimed in claim 1, wherein said rotor (113) comprises at least one threaded cylindrical bore (123) arranged with its axis lying in a plane orthogonal to the rotation axis of the rotor (113) and radially relative to said rotor, in which bore additional masses consisting of threaded dowels can be located and displaced in order to reduce the unbalance of said rotating portion
- The pump as claimed in claim 1, wherein the rotating shaft (205) is supported by a pair of rolling bearings (207) and is driven by an electric motor (211), the bearings and the motor being located in a pump region that is axially separated from the pumping region where the rotor (213) is housed.
- The pump as claimed in claim 8, wherein a pair of displacement sensors (221A, 221B) is provided in the basement (203) of the pump (201), opposite the rotating shaft (205) thereof and at opposite sides of the rotor (209) of the electric motor (211).
- The pump as claimed in claim 1, wherein said displacement sensors are eddy current displacement sensors.
- The pump as claimed in claim 10, wherein said sensors comprise a coil (53) in which a high frequency AC current generating a variable magnetic field flows.
- The pump as claimed in claim 11, wherein said sensors comprise an impedance-to-voltage converter (61), such that a variation in the voltage level of an output signal of said converter (61) corresponds to an impedance variation in the coil of said sensor.
- The pump as claimed in claim 12, wherein said sensors (121A - 121D; 221A, 221B) provide, during pump operation, a signal representative of the displacement of the rotating portion relative to the stationary portions.
- The pump as claimed in claim 1, wherein said pump is a turbomolecular pump.
- A method of balancing a rotary vacuum pump of the kind comprising a stationary portion (103; 203) and a rotating portion comprising a rotating shaft (105; 205) equipped with a rotor assembly (113; 213) for gas pumping when co-operating with a stator assembly, said rotating shaft being driven by an electric motor (111; 211) and being supported by at least one rolling mechanical bearing (107; 207) relative to said stationary portion, the method comprising the steps of:a) providing a vacuum-tight bell (119; 219) in which the pump can be housed during balancing;b) coupling said pump, without said stator assembly, to said bell;c) making vacuum in said bell;d) driving said rotating pump portion into rotation;e) measuring the displacement, at the rotation frequency, of said rotating portion relative to said stationary portion;f) stopping said rotating portion;g) balancing said rotating portion by means of additional masses;h) repeating, if necessary, steps b) to g);
and being characterised in that said displacement measurement is obtained by means of at least two displacement sensors (121A - 121F; 221A - 221F), capable of generating an electrical signal varying with the distance between said stationary portion and said rotating portion during the rotation of said shaft (105; 205) and said rotor assembly (113; 213).
Priority Applications (4)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
DE602004025916T DE602004025916D1 (en) | 2004-07-20 | 2004-07-20 | Rotary vacuum pump and its balancing method |
EP04103445A EP1619395B1 (en) | 2004-07-20 | 2004-07-20 | Rotary vacuum pump, structure and method for the balancing thereof |
US11/184,280 US20060018772A1 (en) | 2004-07-20 | 2005-07-19 | Rotary vacuum pump, structure and method for the balancing thereof |
JP2005208883A JP2006029338A (en) | 2004-07-20 | 2005-07-19 | Rotary vacuum pump, balance regulating structure thereof, and method of regulating balance therein |
Applications Claiming Priority (1)
Application Number | Priority Date | Filing Date | Title |
---|---|---|---|
EP04103445A EP1619395B1 (en) | 2004-07-20 | 2004-07-20 | Rotary vacuum pump, structure and method for the balancing thereof |
Publications (2)
Publication Number | Publication Date |
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EP1619395A1 EP1619395A1 (en) | 2006-01-25 |
EP1619395B1 true EP1619395B1 (en) | 2010-03-10 |
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Family Applications (1)
Application Number | Title | Priority Date | Filing Date |
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EP04103445A Expired - Fee Related EP1619395B1 (en) | 2004-07-20 | 2004-07-20 | Rotary vacuum pump, structure and method for the balancing thereof |
Country Status (4)
Country | Link |
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US (1) | US20060018772A1 (en) |
EP (1) | EP1619395B1 (en) |
JP (1) | JP2006029338A (en) |
DE (1) | DE602004025916D1 (en) |
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DE102008024764A1 (en) * | 2008-05-23 | 2009-11-26 | Oerlikon Leybold Vacuum Gmbh | Multi-stage vacuum pump |
DE102010021241A1 (en) * | 2010-05-21 | 2011-11-24 | Oerlikon Leybold Vacuum Gmbh | vacuum pump |
DE102011105806A1 (en) * | 2011-05-05 | 2012-11-08 | Pfeiffer Vacuum Gmbh | Vacuum pump with rotor |
JP5919745B2 (en) * | 2011-11-15 | 2016-05-18 | 株式会社島津製作所 | Vacuum pump |
DE102013113400A1 (en) * | 2013-12-03 | 2015-06-03 | Pfeiffer Vacuum Gmbh | Pump and method for balancing a rotor |
GB201514001D0 (en) | 2015-08-07 | 2015-09-23 | Edwards Ltd | Pumps |
EP3135919B1 (en) * | 2015-08-24 | 2019-02-20 | Pfeiffer Vacuum Gmbh | Vacuum pump |
US10557471B2 (en) | 2017-11-16 | 2020-02-11 | L Dean Stansbury | Turbomolecular vacuum pump for ionized matter and plasma fields |
CN114216680A (en) * | 2021-11-05 | 2022-03-22 | 上海航天控制技术研究所 | High-speed rotor kurtosis detection fault diagnosis device and method |
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2004
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- 2004-07-20 EP EP04103445A patent/EP1619395B1/en not_active Expired - Fee Related
-
2005
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Also Published As
Publication number | Publication date |
---|---|
US20060018772A1 (en) | 2006-01-26 |
EP1619395A1 (en) | 2006-01-25 |
DE602004025916D1 (en) | 2010-04-22 |
JP2006029338A (en) | 2006-02-02 |
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