PURPOSE: To provide a small size, light weight and simple structure with a low cost by disposing a compressor and an expansion unit at the axial one side of an accelerating mechanism for transmitting the rotary force of a prime mover to the compressor.

CONSTITUTION: An air conditioner system 1 comprises a rotating mechanism 3, a heat exchanger 5 (cooler), an engine 7 (prime mover) and a belt transmission mechanism 9. The mechanism 3 has a planetary gear type accelerating mechanism 19, a centrifugal turbine 21 (expansion unit) and a compressor 23. Thus, the turbine 21 and the compressor 23 are disposed at the axial one side of the mechanism 19 the impellers of the turbine 21 and the compressor 23 can be supported by a cantilever type and supported by a common bearing and hence the axial size can be reduced that much. In addition, the engine 7 can be coupled to the mechanism 19 without using a transmission mechanism like a conventional bent transmission mechanism, and axially and radially reduced in size by the size of the transmission mechanism.