| 摘要 |
PROBLEM TO BE SOLVED: To provide an oilless screw compressor with a reduced power consumption when it is in the no-load operation or low-speed rotation. SOLUTION: The oilless screw compressor 100 comprises a low pressure stage compressor body 1 and a high pressure stage compressor body 2 and operates in two modes in reversals, i.e., a loaded operation in which the air is compressed in accordance with the change of the load and a non-load operation in which the air is released to the atmosphere or the like. The low pressure stage compressor body and high pressure stage compressor body are rotated by a motor 12 driven by an inverter 26 through gears 14, 11A, 11B. At starting or in the no-load operation, low-speed rotation, etc., part of the lubricating oil stored in the lower part of a gear case 3 and fed through an oil cooler 32 is returned to the gear case by opening an oil exhaust solenoid valve 35 installed on an oil supply piping 34B branched from an oil supply piping 34C.
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