| 摘要 |
PURPOSE:To obtain the optimum design volume ratio in accordance with the operating condition by forming a recessed groove penetrating the end faces of the suction side and discharge side in the axial direction on a casing inner-wall and providing the first and second slide valves in series on this recessed groove. CONSTITUTION:A suction pressure Ps and a discharge pressure Pd are detected by a suction pressure sensor 19 and a discharge pressure sensor 20 provided respectively on the suction section and discharge section of a screw-type compressor, they are transmitted to a regulator 21 as an electrical signal, and the optimum value of the design volume ratio capable of obtaining the minimum required power for an operation compression ratio Pd/Ps is calculated. When the suction pressure Ps detected by the suction pressure sensor 19 becomes lower than the preset pressure of the regulator 21, the difference is calculated by the regulator 21, a solenoid-type four-way valve 27 is operated by an electrical signal, an oil pressure is applied to the space 12 of an oil hydraulic cylinder 9 through a pipeline 28, on the other hand, the oil in a space 11 is released to a suction los-pressure section through pipelines 29, 30, thereby only the first slide valve 3 is slid toward a discharge port 16 so as to return the suction pressure Ps to the preset pressure, thus reducing the load. |
