A magnetic bearing device includes first and second radial electromagnets supporting a rotor shaft in a contactless manner in first and second radial directions. A controller controls each of a first excitation amplifier and a second excitation amplifier based on a result of demodulation by each of a first demodulation section and a second demodulation section. The phase of a second carrier signal differs by (/2+) radian from the phase of a first carrier signal. A first demodulation section samples a detection signal of a first current sensor at sampling timing shifted by a phase from timing at which a first carrier signal becomes a peak, and a second demodulation section samples the detection signal of a second current sensor at sampling timing shifted by a phase () from timing at which the second carrier signal becomes a peak.

A vacuum pump and a vacuum pump rotor blade that can effectively limit deposition of reaction products are provided. The vacuum pump includes a rotating shaft held rotationally, a drive mechanism for the rotating shaft, a first rotor blade made of a first material, a second rotor blade made of a second material having higher heat resistance than the first material, and disposed further toward a downstream side than the first rotor blade, and a casing enclosing the rotating shaft, the first rotor blade, and the second rotor blade. The second rotor blade is disposed, via a heat insulating portion, on the first rotor blade.

A vacuum pump includes a housing, a magnetic bearing, and a magnet nut. The magnetic bearing has a first permanent magnet arranged at the periphery of a magnet holder and a second permanent magnet arranged in the rotor to face the first permanent magnet in a radial direction. The magnet nut has a main body portion and protrusions. The main body portion adjusts the position of the first permanent magnet relative to the second permanent magnet by rotating relative to the magnet holder. The protrusion protrudes from an upper surface of the main body portion, and has contact target surfaces contactable with a first tool configured to rotate the main body portion from the upper surface side of the main body portion and contactable with a second tool configured to rotate the main body portion from the outer periphery side of the main body portion.

A magnetic bearing device comprises a first carrier generation section generating a first carrier signal; a second carrier generation section generating a second carrier signal whose phase differs by (/2+) radian from the phase of the first carrier signal; a first demodulation section performing demodulation by sampling the first modulated signal at sampling timing shifted by a phase from timing at which the first carrier signal becomes a peak; a second demodulation section performing demodulation by sampling the second modulated signal at sampling timing shifted by a phase () from timing at which the second carrier signal becomes a peak; and a controller controlling current in each of the first radial electromagnet and the second radial electromagnet, based on a result of the demodulation by each of the first demodulation section and the second demodulation section.

A magnetic bearing device includes a first carrier generation section which generates a first carrier signal, and a second carrier generation section which generates a second carrier signal whose phase differs by (/2+) radian from the phase of the first carrier signal. In addition, the magnetic bearing device includes a first demodulation section which performs demodulation by sampling the first modulated signal at sampling timing shifted by a phase from timing at which the first carrier signal becomes a peak. A second demodulation section performs demodulation by sampling the second modulated signal at sampling timing shifted by a phase () from timing at which the second carrier signal becomes a peak. A controller controls current in each of the first radial electromagnet and the second radial electromagnet, based on a result of the demodulation by each of the first demodulation section and the second demodulation section.

A stator is provided which exerts a combined electromagnetic force of a plurality of electromagnets on a drive shaft having a fluctuating load. A controller is provided which controls a current difference between a first coil current passed through a coil of the electromagnet generating an electromagnetic force in a direction opposite to that of the load and a second coil current passed through a coil of the electromagnet generating an electromagnetic force in the same direction as that of the load to perform a position control on the drive shaft. The controller adjusts the second coil current to reduce an average value of the second coil current.

A method for synchronously inhibiting subcritical vibrations of magnetic levitation molecular pump rotor, by use of synchronously sampling signals of subcritical vibrations of the rotor generated after the rotor of the magnetic levitation molecular pump touches down so as to obtain the amplitude and the phase of subcritical vibrations of the rotor, based on which a compensation force is output for inhibiting subcritical vibrations of the rotor. Through using the present method, an accurate synchronous for signals of subcritical vibrations and fast inhibition for subcritical vibrations of the rotor is achieved.

A magnetic bearing device comprises a controller configured to obtain magnetic levitation information of the rotor shaft by AD sampling of current detection signals from the plurality of current sensors and a sum signal obtained by adding the pair of current detection signals relating to the pair of electromagnets, and perform PWM control of the excitation amplifiers based on the magnetic levitation information. The controller performs PWM control so that a length of one of an on-duty period and an off-duty period of the PWM carrier signal is always longer than a predetermined time period based on an attenuation characteristic of a spike noise produced in the electromagnetic current, and performs the AD sampling after the predetermined time period passes from starting timing of one of the on-duty period and the off-duty period.

The present invention is directed to a magnet for a magnetic bearing arrangement, a bearing arrangement comprising said magnet, and a vacuum pump comprising said bearing arrangement. In particular the invention can be particularly useful in a magnetic bearing arrangement that reduces stray magnetic fields for a turbomolecular vacuum pump, although it is understood that the invention is not limited to this field and other applications will be understood by the skilled person.

The present disclosure relates to a rotor assembly 102 for a turbomolecular pump 100. The rotor assembly 102 comprises a rotor shaft 116, a plurality of rotor blades 126 extending from the rotor shaft 116, and a balancing member 130 fitted within the rotor shaft 116 with an interference fit. The rotor shaft 116 extends along a longitudinal axis 122 about which the rotor assembly 102 is configured to rotate. The interference fit is such that the balancing member 130 is retained in compression by the rotor assembly 102. The present disclosure also relates to a turbomolecular pump 100 including the rotor assembly 102 and a method of assembling a rotor assembly 102 for the same.