| 摘要 |
PURPOSE:To make it possible to improve sealing effect by forming a screw seal portion with spiral grooves over entire inner circumference diameter side length of a sleeve body including its overhang portion which is not inserted into its casing, thereby extending the spiral groove length. CONSTITUTION:As oil which has lubricated a bearing 4 is thrown outside a shown with an arrow 20 due to centrifugal force of a shaft 4 and falls to an oil discharge hole 7 like the oil 23 shown in black in a space 26 on the outer side of a screw seal 15, leakage out of a gap of the seal 15 is restricted. Also, as a long range of screw seal portion including an overhang portion which is not inserted into a casing 1 is formed on the inner circumference of a sleeve body of the screw seal 15, the sealing effect is improved. Accordingly, a spiral groove length can be increased without increasing a span between bearings in the axial direction of an oil-free screw compressor and without narrowing an oil discharge passage. As a result, good sealing effect can be obtained.
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