| 摘要 |
PROBLEM TO BE SOLVED: To obtain a desired tooth form shape at an ordinary temperature, in a screw rotor formed with a tooth form part by coating a synthetic resin around a metal shaft. SOLUTION: When assuming Rda for value excepting a radius Rs of a metal shaft from a distance R from an arbitrary point on the periphery of regular tooth form of a screw rotor to a rotor rotational center axis andΔ, for shrinkage amount,Δ=αk.Rda/(1-αk), where,α; tooth form correction coefficient = Aαcosθ/A; coefficient determined to be related to shape of tooth form,θ; angle formed by normal in one point on a tooth form external shape and a straight line in a rotor radial direction (in the case ofθ>=90 deg., set all toθ=90 deg.), k; shrinkage factor of resin. On a radial line passing through an arbitrary point on the periphery of a regular tooth form, a correction molding die with a point addingΔto the point serving as a tooth form internal periphery is formed, this die is used, the screw rotor is molded.
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