PURPOSE: To prevent the overcooling at the high speed rotation of a car airconditioner, by providing a valve device for controlling the refrigerant flow in the suction path of a compressor.

CONSTITUTION: Under the low speed rotation, the refrigerant gas will flow through the outercircumferential path of a control valve 4 and a hole 4a made in the control valve 4, thereby the suction path having sufficient area can be insured. When the rotation exceeds over the desired level, the refrigerant gas flow will increase to increase the pressure loss across the control valve 4 thus to displace the control valve 4 in the direction of flow. The suction gas path area will decrease as the displacement and when reaching to the desired level, the refrigerant gas will flow only through the hole 4a thereby the overcooling of a compressor for a car airconditioner can be prevented.