Abstract: A gas turbo pump assembly for connection to a port of a vacuum chamber and having high throughput with low vibration. The assembly comprises a turbo pump and a vibration damper. The pump has a pump body with an external surface and a center axis defining a first axial end and a second axial end of the pump. The pump also has a pump inlet port, the inlet port being coupled to the vacuum chamber port disposed at the first axial end of the pump, and an exit port disposed proximate the second axial end of the pump. The assembly vibration damper is structured to enclose a substantial portion of the pump in a nested arrangement.

Abstract: A vacuum pump includes a housing, a rotor located in the housing and having a shaft and pump-active elements supported on the shaft, a stator having pump-active elements and located in a separate housing part of the housing, for driving the pump, bearings for rotatably supporting the rotor shaft, and at least one vacuum chamber located in the housing.

Abstract: An apparatus and method for differential pumping of a mass spectrometer or other ion-optical device provides a transverse pressure drop introduced across a face of a primary rotor of a turbomolecular pump by placement of one or more partitions in close proximity to the face of the primary rotor. Thus, two or more regions of space within the vacuum chamber having respective different pressures is achieved with a single pump.

Abstract: A multi-chamber installation (1) treats objects under vacuum. An evacuation system (5) is connected to a plurality of chambers (2, 3, 4). To reduce the complexity of the evacuation process, a forepump (5) has several stages (11, 12, 13). Each of said stages is connected to one of the chambers (2, 3, 4).

Abstract: The present invention relates to vacuum pumps and a method for creating and maintaining a high vacuum. A vacuum pump includes a regenerative section and a turbo-molecular section. A common first rotor carries forward-rotating elements of both the regenerative section and the turbo-molecular section. Additionally, a second rotor carries counter-rotating elements of the turbo-molecular section. A first drive rotates the first rotor in a forward rotational direction while a second drive rotates the second rotor in a counter-rotational direction. The drives may be controlled to drive the common first rotor on start-up, and to later drive the second rotor.

Abstract: The present invention relates to the integration of a TMP with the associated bypass line and valves so that a single sub-assembly is created. The housing of the TMP is significantly modified to accommodate the associated equipment necessary for constructing a high-vacuum system.

Abstract: A mechanical vacuum pump includes a rotor made of a light metal alloy by powder metallurgy. The powder metallurgy increases the resistance of the rotor to heat and creep.

Abstract: A turbomolecular pump (10) comprises a stator (12, 18), a pump rotor (20) a motor (28) for driving the pump rotor and a control device (42). The control device (42) controls the motor output power such that the motor output power does not exceed a permissible maximum motor output power. On the stator side of the turbomolecular pump (10), temperature sensors (32–38) for measuring the stator temperature are arranged. The control device (42) comprises a maximum output power detecting device (50) that determines the permissible maximum motor output power in dependence on the measured stator temperature. Thus, the permissible maximum motor output power is not set to a constant value but always fixed in dependence on the current, measured stator temperature. Thereby, the capacity of the motor can be fully utilized as long as the measured stator temperature lies below a maximum value.

Abstract: In a turbo-molecular pump with a high vacuum-side induction area and of a rotational symmetrical arrangement, comprising a compressor turbine including a rotor and a stator tube having axially alternately tightly arranged rotor blade rings and stator vane rings with oppositely oriented blade and vane surfaces, a pre-vacuum chamber with a gas guide structure for the connection of a pre-pumping system, a drive module and a bearing unit, the turbo-molecular pump has a center area with a central coaxial open space extending from an ambient end to the high vacuum-side induction area and the open space is closed at its end adjacent the ambient end thereof by a flange in a vacuum-tight manner or is connected to a vacuum recipient, and the high-vacuum end of this space is separated from a pre-vacuum space.

Abstract: A molecular pump has a casing having a gas inlet port and a gas discharge port, a stator disposed within the casing, a shaft disposed in the casing concentrically with the stator, a bearing rotatably supporting the shaft for undergoing rotation relative to the stator in a preselected direction of rotation, a rotor mounted on the shaft for rotation therewith in the preselected direction of rotation, and a motor for rotationally driving the shaft. A flange is connected to the casing at the gas inlet port.

Abstract: A vacuum pump system includes at least one high-vacuum pump, a fore-vacuum pump, and at least one intermediate pump, arranged between the at least one high-vacuum pump and the fore-vacuum pump and having its inlet connected directly and exclusively with the outlet of the high-vacuum pump.

Abstract: An ultra-high speed vacuum pump evacuation system includes a first stage ultra-high speed turbofan and a second stage conventional turbomolecular pump. The turbofan is either connected in series to a chamber to be evacuated, or is optionally disposed entirely within the chamber. The turbofan employs large diameter rotor blades operating at high linear blade velocity to impart an ultra-high pumping speed to a fluid. The second stage turbomolecular pump is fluidly connected downstream from the first stage turbofan. In operation, the first stage turbofan operates in a pre-existing vacuum, with the fluid asserting only small axial forces upon the rotor blades. The turbofan imparts a velocity to fluid particles towards an outlet at a high volume rate, but moderate compression ratio. The second stage conventional turbomolecular pump then compresses the fluid to pressures for evacuation by a roughing pump.

Abstract: A vacuum pump apparatus has a casing and a base connected to the casing. The base has an opening communicating with an interior space of the casing. A heater is mounted on the base for heating the base to maintain a gas discharge path at a temperature high enough to prevent solidification of processed gas in the vacuum pump. A cover member covers the opening of the base. The cover member has a first surface communicating with the interior space of the casing and a second surface exposed to the exterior of the vacuum pump. A substrate is connected to the first surface of the cover member and has at least one circuit for controlling operation of the vacuum pump.

Abstract: A method and apparatus for monitoring operating characteristics and/or control signals of a system comprising a variable speed vacuum pump. Operating characteristics and/or control signals of the system may be monitored, and the pumping speed of the variable speed vacuum pump may be altered responsive to the monitored operating characteristics and/or control signals.

Abstract: A vacuum pump (1, 30) has an inlet (5) and an outlet (6). Plug-in screw fittings (9) are connected with the inlet and the outlet. The plug-in screw fittings include a bore with an internal bevel (22) that receives a flexible connecting line (23), a chuck collet (19), and an O-ring (21) frictionally in a vacuum-tight relationship. In this manner, a more simple and versatile connection is provided between the vacuum pump and the connecting lines.

Abstract: A vacuum system comprises, as an integral assembly, a vacuum pump with drive motor, a purge valve, a roughing valve and an electronic control module. A cryogenic vacuum pump and a turbomolecular vacuum pump are disclosed. The control module has a programmed processor for controlling the motor and valves and is user programmable for establishing specific control sequences. The integral electronic control module is removable from the assembly and is connected to the other devices through a common connector assembly. In the turbomolecular pump system proper introduction of a purge gas through the purge valve is detected by detecting the current load on the pump drive or by detecting foreline pressure. To test the purge gas status, the purge valve may be closed and then opened as drive current or pressure is monitored. After power failure, the controller will continue normal drive of the turbomolecular pump so long as the speed of the pump has remained above a threshold value.

Abstract: Provided is a connecting structure for a vacuum pump, which can block propagation of electrical noise, generated by a main body of the vacuum pump. Between both ends of a connection piping for connecting the vacuum pump to a vacuum chamber of an apparatus to be connected with and evacuated by the vacuum pump, there is interposedly provided an electrical insulating portion formed of an insulating material so as to provide electrical insulation therebetween. The electrical insulation portion may be provided to a connection piping member such as a damper (or a valve depending on the connection arrangement) for absorbing mechanical vibrations.

Abstract: A rotor (12) is mounted in a stator (14) with radial magnetic bearings (16, 19) and with an axial magnetic bearing (40) in a contactless manner. The axial magnetic bearing (40) produces an axial magnetic field with a magnet coil (40) and a yoke iron (44) mounted on the stator (14). An axially magnetized permanent magnet (50) is provided on the rotor (12), located approxaimately axially opposite the yoke iron (44). A permanently axially magnetized compensating magnet (54) is provided on the stator (14) and arranged axially opposite the permanent magnet of the rotor (50) and polarized in the opposite direction, such that the permanent magnet (50) of the rotor and the compensating magnet (54) repel each other. In a center position, the rotor is bias-free by compensating the forces of attraction between the permanent magnet of the rotor and the yoke iron. As a result, the center position of the rotor can be adjusted with relatively small magnet coil flows.

Abstract: A molecular drag vacuum pump for pumping a gas from an inlet to an outlet includes a high-speed spinning disk disposed within a housing. Gas flows through passageways in the housing adjacent the disk, where it comes into contact with surfaces of the spinning disk. Conformable wipers direct the gas to successive stages adjacent the disk. The pump can be powered by an integrated motor, comprising permanent magnets in the disk and cooperating coils in the housing. The pump can include various features, such as ridges on the wipers, seal rings, and regenerative pumping pockets, to reduce leakage and prevent backflow. The housing can have a modular configuration to allow two or more pump modules to be connected and operate in series. Successive modules may be independently or commonly powered, and may counter-rotate.

Abstract: A compact turbomolecular vacuum pump (1) is driven by a cup-type motor (8). The cup-shaped rotor of the motor is preferably integrated into the pump rotor (14) and may define corresponding pumping stages, for instance Holweck stages, wherein the stators (11, 12) of said stages being preferably obtained by superimposing stator rings (11′, 12′).

Abstract: A turbomolecular pump including a housing having a suction opening and a gas outlet opening, and a plurality of alternatingly arranged one behind another, stator and stator rings provided, respectively with support rings for supporting each a blade, with a support ring of a stator disc located adjacent to a high pressure region of the turbomolecular pump being connected with an adjacent housing part over a large surface or being formed with the adjacent housing part as one-piece part.

Abstract: A molecular drag, turbomolecular, or hybrid turbo/drag pump (5) of the invention has an outlet stage with a cylindrical peripheral wall (17) and a radial outlet orifice (23) passing through the cylindrical peripheral wall (17). An annular coaxial closure member (24) bears against the cylindrical peripheral wall (17) around the radial outlet orifice. The annular coaxial closure member (24) includes a through slot and optionally also a total closure shutter (26). The annular coaxial closure member (24) is caused to turn about the axis of the cylinder by a motor (8) in order to place its through slot or its total closure shutter (26) in register with the radial outlet orifice (23), or partially in register with the radial outlet orifice (23) in order to adjust the opening of the valve and regulate the gas flow pumped by the pump (5). A pump is thus provided that includes an integrated regulator and/or closure valve.

Abstract: A compact turbo-molecular pump having a high depressurizing capability. A motor for rotating a rotor vane includes an air bearing. The air bearing has a rotary cylinder and a fixed surface surrounding the rotary cylinder. The material of the rotary cylinder has a coefficient of thermal expansion that is smaller than that of the material of the fixed surface. Thus, change in the dimensions of the rotary cylinder is smaller than that of the fixed surface even if the temperature of the air bearing rises during operation of the pump. Thus, the rotary cylinder avoids contact with the fixed surface.

Abstract: A vacuum pump (1) includes a housing (2) in which a suction inlet opening (5) is defined. A vibration absorber (7) includes a suspension body (8) and an absorber jacket (9). The housing (2) of the vacuum pump (1) is connected directly to one end of the suspension body (8) in vacuum-tight connection and an opposite end of the suspension body carries a connecting port (14). By connecting the suspension body directly with the housing without mechanically releasable interconnection elements, the overall height of the pump and suspension body assembly is reduced.

Abstract: A vacuum pump is capable of preventing reaction products produced by a process gas from being precipitated in the pump, of holding various pump components in an allowable temperature range, and hence of operating in a wide operation range, and which has increased durability. The vacuum pump has a pump casing having an intake port and an exhaust port, an exhaust assembly disposed in the pump casing and having a rotor and a stator, and a heating unit for heating a stator side component of the exhaust assembly positioned near the exhaust port. The heating unit is disposed in a space inside the pump casing where is evacuated during operation, and held in contact with at least a portion of the stator side component of the exhaust assembly positioned near the exhaust port.

Abstract: A turbomolecular pump (10) comprises a stator, a pump rotor, a motor (28) for driving the pump rotor and a control device (42). The control device (42) controls the motor output power such that the motor output power does not exceed a permissible maximum motor output power. On the stator side of the turbomolecular pump (10), temperature sensors (32-38) for measuring the stator temperature are arranged. The control device (42) comprises a maximum output power detecting device (50) determining the permissible maximum motor output power in dependence on the measured stator temperature. Thus, the permissible maximum motor output power is not set to a constant value but always fixed in dependence on the stator temperature. Thereby, the capacity of the motor can be fully utilized as long as the measured stator temperature lies below a maximum value.

Abstract: In a flange 61 provided at the suction port of a molecular pump, a hollow portion 72 is provided adjacently to a bolt hole 14. The hollow portion 72 is a through hole penetrating the flange 61. Thereby, a thin-walled portion 71 is formed between the bolt hole 14 and the hollow portion 72. If a shock in the direction of rotation of a rotor portion is provided to the molecular pump, for example, by the destruction of the rotor portion, the flange 61 slides in the direction of rotation of the rotor portion together with the molecular pump. Thereupon, a bolt fixing the flange 61 to a flange of a vacuum system hits the thin-walled portion 71, so that the thin-walled portion 71 is plastically deformed in the direction of arrow B. Thus, by the plastic deformation of the thin-walled portion 71, energy for rotating the molecular pump is consumed as energy for plastically deforming the thin-walled portion 71, so that the shock provided to the molecular pump is cushioned.

Abstract: The invention provides a rotor for a turbo/drag vacuum pump, the rotor comprising an upstream rotor segment of the turbine type made of metal or alloy, and a downstream rotor segment of Holweck type made of composite material. The downstream segment of the rotor has a reinforcing structure made of long fibers that are distributed in a manner that varies as a function of the section under consideration: in the annular connection region connected to the upstream segment of the rotor, the fibers are inclined and/or spaced apart in order to conserve sufficient flexibility for the composite material to enable it to deform so as to track deformation of the metal of the upstream rotor segment while it is in operation; in contrast, the fibers are close together and form turns that touch in the downstream region of the skirt, thereby guaranteeing greater stiffness in order to withstand the mechanical stresses that occur during high-speed rotation of the rotor in operation.

Abstract: A cascade type pump arrangement for a particle beam device has first and second turbomolecular pumps, wherein an outlet of the second turbomolecular pump is forepumped by an intermediate pressure region situated between a main pump port and an outlet of the first turbomolecular pump. The particle beam device has a particle beam source operated in ultra high vacuum and a specimen chamber operated at pressures from high vacuum at least up to 1 hPa.

Abstract: A seal is disposed between a rotating part and a stationary part. At least one of the parts is provided with projections which protrude into the seal gap. The seal gap (5) extends approximately radially so that both parts are provided with projections which extend in an axial direction, which are located concentrically in relation to the axis of rotation of the rotating parts and which engage with each other. Said projections are configured in the form of rows of blade-like elements. This effectively seals approximately radially extending seal gaps.

Abstract: A vacuum pump has a casing having an inlet port and an outlet port, a flange integral with the casing and having a peripheral inner surface defining the inlet port and an end surface for connection to a container to be evacuated, and exhaust means for drawing in a gas through the inlet port and discharging the gas through the outlet port. A coating of material having low heat conductivity is disposed on the end surface of the flange.

Abstract: To provide a small vacuum pump making it possible to efficiently perform evacuation from the atmosphere to a high vacuum (degree of vacuum: 10−5 Pa) by using a single pump unit. A turbo-molecular pump mechanism portion is arranged on the high-vacuum side, a volute pump mechanism portion is arranged on the atmosphere side, and a thread groove pump mechanism portion is arranged between the turbo-molecular pump mechanism portion and the volute pump mechanism portion. Further, rotor blades of the turbo-molecular pump mechanism portion, a rotor of the thread groove pump mechanism portion, and an impeller of the volute pump mechanism portion are integrally mounted to a single rotor shaft, which is rotated by a single motor.

Abstract: A compact turbo-molecular pump having a high depressurizing capability. A motor for rotating a rotor vane includes an air bearing. The air bearing has a rotary cylinder and a fixed surface surrounding the rotary cylinder. The material of the rotary cylinder has a coefficient of thermal expansion that is smaller than that of the material of the fixed surface. Thus, change in the dimensions of the rotary cylinder is smaller than that of the fixed surface even if the temperature of the air bearing rises during operation of the pump. Thus, the rotary cylinder avoids contact with the fixed surface.

Abstract: In a vacuum pumping system according to the invention, the Roots or claw multistage dry primary pump discharges into an outlet stage including an additional piston or membrane pump connected in parallel with a preliminary evacuation pipe including a check valve. The outlet stage very significantly reduces heating of the primary pump and thereby enables the vacuum pumping system to pump efficiently and without damage gases with a low thermal conductivity, such as argon or xenon.

Abstract: A gas friction pump, including a housing having a suction opening, a gas outlet opening, and a plurality of rotatable and stationary components arranged in the housing and having a pump-active structure for pumping gases and maintaining a pressure ratio, and an additional gas inlet formed as a longitudinal opening extending, in a longitudinal direction thereof, over a portion of an outer edge of a rotatable component.

Abstract: The present invention provides a turbo molecular pump capable of suppressing temperature rise in an electronic circuit section within a range, without losing airtight property thereof with a simple construction. In a base section of a turbo molecular pump, a bottom portion thereof is sealed by a bottom cover. A semiconductor device is disposed at the inner portion of the bottom cover. A cooling member is provided, which is used for releasing heat of the semiconductor device in an airtight state outside the bottom cover.

Abstract: A molecular vacuum pump (1) has a stator unit (9) and a rotor unit (8) disposed within a housing (2). A narrow gap is maintained during operation between the stator unit (9) and the rotor unit (8). The stator unit (9) and the rotor unit (8) are coupled together with respect to vibration to form a rotor/stator system (3). Elastic vibration elements (4, 5) mount the rotor/stator system in the housing such that the rotor/stator system rotates as a unit relative to the housing. Because the rotor and stator units vibrate together rather than relative to each other, very small, precise tolerances are maintained between them.

Abstract: A gas friction pump including a housing (1) having a suction opening (2) and a gas outlet opening (3), rotor (12) and stator (14) components arranged in the housing (1) for delivery of gases and for obtaining a pressure ratio; and an additional, at least one-stage, concave pump unit (20, 30, 40) provided at a side of the suction opening (2) and having a gas delivery structure, with the additional pump unit (20, 30, 40) being so formed that gas delivery takes place in a radial direction, and with rotor components (21, 31, 41) of the additional pump unit (20, 30, 40) being supported on the same rotor shaft (4) as the rotor components of the pump itself.

Abstract: The vacuum pump (10) comprises a stator (14) in which a rotor (12) with radial magnetic bearings (16,19) and with an axial magnetic bearing (40) is mounted in a contactless manner. The axial magnetic bearing (40) produces an axial magnetic field by means of a magnet coil (40) with a yoke iron (44) on the stator (14). An axially magnetized permanent magnet (50) is provided on the rotor (12), located approximately axially opposite the yoke iron (44). A permanently axially magnetized compensating magnet (54) is provided on the stator (14) and arranged axially opposite the permanent magnet of the rotor (50) and polarized in the opposite direction, whereby the permanent magnet (50) of the rotor and the compensating magnet (54) repel each other. In a centre position, the rotor is bias-free by compensating the forces of attraction between the permanent magnet of the rotor and the yoke iron. As a result, the centre position of the rotor can be adjusted with relatively small magnet coil flows.

Abstract: A heater 29 is mounted on the outer peripheral surface of a base 6 to heat the base 6. By heating the base 6, the interior of a gas discharge path for process gas is kept at a high temperature, and hence the precipitation of solid product in the pump is restrained. Also, a pump inside substrate 25 in which various types of information on a vacuum pump are stored is arranged on the inside of a back cover 26. A water cooled tube 30 is installed on the back cover 26 on which the pump inside substrate 25 is arranged, whereby the back cover 26 is cooled forcedly. Further, a heat insulating material 27 with low heat conductivity is arranged in a connecting portion 27a and a contacting portion 27b between the back cover 26 and the base 6. By constructing the vacuum pump in this manner, the pump inside substrate 25 can be cooled efficiently while the gas discharge path for process gas in the vacuum pump is kept at a higher temperature than before.

Abstract: A heater 29 is mounted on the outer peripheral surface of a base 6 to heat the base 6. A heat shutoff wall 24b is provided on a motor housing 24 to prevent the radiation heat of the base 6 heated by the heater 29 from transferring to a pump inside substrate 25. A gap portion 27 is formed by providing a gap between the motor housing 24 and the base 6 to prevent the heat of the base 6 heated by the heater 29 from transferring to the motor housing 24. Also, a water cooled tube 28 is installed under the motor housing fixing portion 24c and cooling water is circulated in the tube to efficiently cool the pump inside substrate 25. By constructing a vacuum pump in this manner, the accumulation of solid product of process gas in the vacuum pump is restrained, and thus the pump inside substrate can be cooled efficiently.

Abstract: A vacuum pump has a cylindrical base member including a groove spacing between the inner and outer peripheries thereof. Accordingly, when the rotor is broken and part of the rotor collides with the inner peripheral portion of the base member during the operation of the vacuum pump, a thicker part of the base member arranged more inside than the groove spacing in the pump case becomes plastically depressed toward the groove spacing by the impact to absorb the rotational collision energy of the rotor.

Abstract: The invention relates to a machine (1), comprising a stator and a rotor (2) which is mounted with radially stable and axially unstable magnetic bearings (3, 4). Said magnetic bearings (3, 4) each consist of concentrically arranged magnetic ring sets (5, 6; 7, 8) in which the stationary magnetic ring set (5 or 7) is situated inside and the rotating magnetic ring set (6 or 8) is situated outside. The machine also comprises means (21, 23, 24, 27) for regulating the axial position of the rotor (2). The aim of the invention is to simplify a machine of this type. To this end, one (4) of the two magnetic bearings (3, 4) is itself equipped with the axial regulation means and at least one coil (23) controlled by a position sensor (21) and pole components (24) surround the outer magnetic ring set (8) of the axially regulated bearing (4).

Abstract: A pump apparatus in accordance with the present invention is used to discharge a process gas from, for example, a semiconductor manufacturing system, and is constructed so that a rotor is pivotally supported by a magnetic bearing. To decrease the solidification and deposition of process gas in a tube of the pump apparatus, heat is generated in a bearing electromagnet of magnetic bearing to keep the temperature of tube at a high temperature. Heat is generated in the bearing electromagnet, for example, by causing a bias current to flow together with a control current, or by causing a high frequency current to flow. Also, a motor is heated by repeating the increase and decrease of rotational speed of motor, whereby the temperature of tube can be raised.

Abstract: A vacuum pump capable of controlling a gas sucking performance is provided. A conductance variable mechanism (50) is arranged at an inlet port (16) formed inside a flange (11). The conductance variable mechanism (50) allows the area of a cross-section of the inlet port to be increased or decreased relative to the direction where gas is fed, so that an amount of gas to be sucked from the inlet port (16) can be controlled.

Abstract: A turbomolecular pump has rotor blades and at least one pair of electromagnets for levitating the rotor blades and for controlling one of a radial position and an axial position of the rotor. A current supplying device supplies a current to the electromagnets. A detecting device detects a current flowing through the electromagnets. A stopping device stops the supply of current to the electromagnets by the current supplying device when a duration of time during which the current detected by the detecting device exceeds a preselected current value is greater than a preselected duration of time.

Abstract: A vacuum pump comprises a pump case having an interior space, a rotor disposed in the interior space of the pump case, and a thread stator disposed in the interior space of the pump case and opposite to an outer peripheral surface of the rotor. At least one heater is arranged in the thread stator for heating the interior space of the pump case. An output device outputs a parameter constituting a factor for determining a temperature of the rotor. A memory stores a database containing information corresponding to a relationship between the parameter output by the output device and a preselected temperature of the heater. A controller inputs the parameter output by the output device and selects from the database stored in the memory the preselected temperature of the heater in accordance with the input parameter.

Abstract: The invention relates to a seal between a rotating part and a stationary part. At least one of the parts is provided with projections which protrude into the seal gap. According to the invention, the seal gap (5) extends approximately radially so that both parts are provided with projections which extend in an axial direction, which are located concentrically in relation to the axis of rotation of the rotating parts and which engage with each other. Said projections are configured in the form of rows of blade-like elements. This provides an effective means of sealing approximately radially extending seal gaps.

Abstract: There is provided a vacuum pump which suppresses the propagation of vibrations to an external container without the use of a damper. The vacuum pump has an outer cylindrical portion, a rotor portion and a stator portion accommodated within the outer cylindrical portion to define a transferring portion for a gas sucked from an inlet port, a magnetic bearing for supporting the rotor portion with respect to the stator portion, a motor for rotating the rotor portion with respect to the stator portion, and a base for supporting the outer cylindrical portion and the stator portion. A vibration absorbing member is interposed between the stator portion and the base, which has a natural frequency F=(f1+f3)/2±(f1−f3)/4, provided that f1, f2 and f3 respectively denote a natural frequency of nutation in conical mode, a natural frequency in parallel mode and a natural frequency of procession in the conical mode, when the rotor portion is rotated at a rated speed.

Abstract: A clearance between a rotor and a stator is adjusted by forming the outer peripheral surface of the rotor and the inner peripheral surface of the stator into a conical shape, and relatively moving the rotor and the stator in the thrust direction. When the rotor is rotatably supported by a magnetic bearing, the magnitude of the clearance between the rotor and the stator may be adjusted by offsetting the position at which the rotor is held in the thrust direction. The stator may be moved in the thrust direction by forming the bottom of the stator of electrostrictive material and expanding and contracting the electrostrictive member. When the outer peripheral surface of the rotor and the inner peripheral surface of the stator is cylindrical, the inner diameter of the stator may be increased and decreased by forming a part of the stator of electrostrictive material.