The suction port on the intake side of a screw-type compressor must be designed so that the compression chamber can inhale sufficiently. Unlike reciprocating compressors, screw-type compressors do not have intake and exhaust valve assemblies; instead, their intake is regulated solely by the opening and closing of a control valve. When the rotors rotate, the space between the grooves of the main and secondary rotors reaches its maximum volume as it turns to align with the intake port opening on the end wall. At this point, the space in the rotor grooves communicates freely with the outside air through the intake port. Since all the air in the grooves has been completely discharged during the exhaust phase, the grooves are in a vacuum state at the end of exhaust. As the rotors turn towards the intake port, external air is drawn in and flows axially into the grooves of the main and secondary rotors. When the grooves are fully filled with air, the intake-side face of the rotors moves away from the intake port of the casing, thereby sealing the air within the grooves.