This invention relates to a variable unit used for compressors in which the ball internal cavity has a piston, a dial and a spindle, the piston is chain with the dial cylinder hinge via the central pin, the angle of piston pin axis with the spindle axis is equal to that of the dial pin shaft axis with the spindle axis. The three of them are all through core of the ball internal cavity to reach the following result: when the drive spindle is, piston and dial always periodically vibrate relatively around the central pin axis without evident moving elements causing vibration working chamber V1 ans V2 alternately induct, compress and exhaust once when the spindle rotates every two periods. |