An electric turbo compressor is an
air compressor to be used in a fuel
cell system, and includes a housing comprised o a compression casing, a motor casing, and a canceller casing, and the housing houses therein an
impeller, a rotary shaft, a thrust canceller (a load cancellation section), and a
motor unit. The rotary shaft is supported by a thrust
air bearing in its thrust direction, and is axially supported by a radial
air bearing in its rotating direction. A thrust load is generated at the rotary shaft when the number of rotations of the
impeller increases. The pressure of the
compressed air acts to the pressure chamber from the
compressed air lead-out section of the compression casing via the
compressed air passage, and this pressure acts on the canceller
flange of the canceller shaft so as to generate a load towards the rear of the rotary shaft. Therefore, the thrust load is cancelled out.