The STP pump (Figure 8) is configured so that rotor blade (1) and stator blade (2) are aligned
alternately in the axial direction. Gas molecules are pumped from the inlet port to the outlet port by
the high speed rotation of the rotor.
The rotor blade (1) is supported by the magnetic bearing without mechanical contact. Therefore, the
STP pump requires no lubrication oil unlike conventional turbomolecular pumps using ball bearings.
The magnetic bearing consists of 5 pairs of active magnetic bearings. The rotor is supported in the
radial direction by 4 pairs of radial direction active magnetic bearings that consist of radial sensor (3)
and radial electromagnet (4). A pair of axial direction active magnetic bearings consists of axial
sensor (5) and axial electromagnet (6) to support the rotor in the axial direction. Because the rotor is
supported without mechanical contact, it can rotate at low vibration.
There is less heat generated from magnetic bearings because there is no friction. Therefore, the STP
pump requires no cooling. However, the STP pump does require water-cooling or air-cooling during
baking and gas pumping. Taking into consideration an unexpected failure of magnetic bearings,
touch down bearings (7) coated with solid lubrication have been installed. They do not contact with
the rotor during the rated operation.
A radial sensor, an axial sensor, a rotation sensor and a temperature sensor always monitor the
magnetic bearing as well as the rotor. If an abnormality/error occurs, the rotor will stop.
1.8 Temperature management system
The Temperature Management System (TMS) maintains the temperature of the turbomolecular
pump by monitoring the temperature using a thermistor in the base of the turbomolecular pump, and
performing the TMS valve and base heater ON/OFF control.
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