| 摘要 |
PURPOSE:To aim at simplifying the control of volume, by providing such an arrangement that a suction port is communicated with a discharge port through shut-off valve, an intermediate port which offers an intermediate pressure between the pressures of suction and discharge ports, is communicated with the suction port through another shut-off valve, and both shut-off valves are selectively opened and closed in accordance with loads. CONSTITUTION:A discharge casing 11 is formed with an intermediate port 12 communicating between a male rotor 3 and a compression space, and a suction casing 9 is formed with an auxiliary suction port 13 opened to a suction port 6' which is communicated with an end wall suction port 6. The intermediate port 12 is communicated with the auxiliary suction port 13 through an automatic valve 14, and an auxiliary discharge port 15 opened to a discharge hole 7' which is communicated with an end wall discharge port 7 formed in the discharge casing 11, is communicated with the auxiliary suction port 13 through an automatic valve 16. When the automatic valve 16 is closed and the automatic valve 14 is opened upon partial load operation, working fluid under intermediate pressure is taken out from an end wall intermediate port 17, and is sucked into the end wall suction port 6 through the suction port 6' after passing through the intermediate port 12, the automatic valve 14 and the auxiliary suction port 13. Thereby, the discharge amount of working fluid is reduced. Accordingly, the control of volume is made possible with an extremely simple structure. |
