| 摘要 |
PURPOSE:To suppress leakage from a part between a rotor and the internal wall of a housing, by symmetrically constituting an external shape of the rotor with respect to an x-axis and a y-axis about its rotary center serving as the original point while forming the rotor in a shape that three circular arc curves of specific shape are respectively continued by a straight line. CONSTITUTION:A rotor 2 symmetrically constitutes its external shape respectively with respect to an x-axis and a y-axis about the rotary center serving as the original point O. And when assumed L for distance between axes of the paired rotors 2, 2, C for clearance between a rotor end part 2a and the internal wall of a housing 1 and R=L/2, in a region of x>=0, y>=0, a circular arc curve I with the original point O serving as the center further with a radius r=2<1/2>/8piR-C+R, conventional involute curve II'' and a curve III', shown by an expression x=LcosQ-(r+C)cos(beta-2Q), y=LsinQ+(r+C)sin(beta-2Q), where beta=sin<-1>x1/r when assumed x1 for x-coordinate of a point where said circular arc curve finishes, are successively formed respectively by linear parts II', III'', thus preventing leakage from a part between the rotor 2 and the internal wall side of the housing 1.
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