SCREW FLUID MACHINE

PURPOSE:To make it possible to simply and surely synchronize the rotations of a pair of rotors with each other by detecting a difference in rotational phase between the pair of rotors which are provided with male and female screw rotors, respectively, and the like, and by controlling the drive of the rotors so that the difference in rotational phase is maintained within a predetermined range. CONSTITUTION:A pair of rotary encoders 18A, 18B detect the rotating angles and rotational speeds of a pair of rotors 2A, 2B, respectively, and deliver their detection signals to a control circuit 5 through a pair of detecting circuits 3A, 3B. Then, the control circuit 5 obtains a difference in rotational phase and a difference in rotational speed between the rotors 2A, 2B, and picks up a rotational speed set previously in an instruction circuit 21 so as to determine a rotational speed instructing value for the rotors 2A, 2B. In accordance with this instructing value, a pair of drive circuits 6A, 6B drive a pair of motors 13A, 13B, respectively. As a result, of the motors 13A, 13B, the one having a higher rotational speed is retarded while the one has a lower rotational speed is made faster. Thereby it is possible to rotate both rotors in synchronization with each other.