SCREW COMPRESSOR

PURPOSE:To reduce the lowering of capacity of a screw compressor due to leakage, by incorporating a slide valve on the suction side of the compressor to reduce the deformation of the discharge side having no slide valve upon deformation of a casing due to the internal pressure, and to maintain the gap between the rotor and the discharge side of the casing to be small. CONSTITUTION:A casing 3 is formed therein with a suction hole 14 communicated with a compression chamber 13 and a discharge hole 19 communicated with a rear casing 5, and a slide valve 16 for constricting an air passage is disposed in the suction hole 14. This slide valve 16 is moved in the axial direction by means of a shaft 19 which is driven by a drive source which is not shown. With this arrangement, even if the casing is deformed due to the internal pressure, the suction side incorporating the slide valve 16 is largely deformed, but the deformation of the discharge side having no slide valve may be made to be less. Therefore, the gaps between the male and female rotors 1, 2 and the discharge side of the casing 3 may be maintained to be less, thereby it is possible to reduce the lowering of capacity of the compressor due to leakage.