| 摘要 |
PROBLEM TO BE SOLVED: To provide a screw machine capable of effectively preventing seizure between rotors even if in high speed continuous operation for a long time as well as improving a performance by narrowing an engaging clearance between the screw rotors. SOLUTION: In a pair of female and male screw rotors 21 and 22 wherein screw gears 211 and 221 having spiral gear tip surface parts 211a and gear root surface parts 211c are disposed, pitch circumferential parts 211p and 221p are disposed as circular arcs within a prescribed angleθ3 having a constant radius rp on an optional cross section, between the gear tip surface part 211a and 221a and the gear root surface parts 211c and 221c of the screw gears 211 and 221. When they are engaged with rotors 22 and 21 of counterparts, respective radiuses of the pitch circumferential parts 211p and 221p are set so as to form a clearance g1 between the pitch circumferential parts 211p and 221p in the engaging clearances of the female and male screw gears 211 and 221 smaller than the other clearances g2, g3 and g4.
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