スライダを用い定速下降させたPEDb200UとPEDb300Uのねじ締め

概要

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PEDb200U and PEDb300U are electric screwdrivers, which are developed for watch makers and fasten a screw with a small torque from 100 to 300 gf・cm at a high revolution rate from 1300 to 3100 rpm. We have studied their characteristics the year before last. Then we moved driver mechanics down manually using a drill stand. Both move down speed and axial force on the screw varied by every measurer, and it might influence the result. Therefore we made up a slider, mounted a driver mechanics on it, and move it down at a given speed. By using the slider, we can fasten a screw without applying an axial force on it. And we obtained different results from those before. A ratio of loosening torque to final torque Tj/T_<fin> takes a value independent of both setting torque and bit revolution rate. They are 60.0 and 63.3% for PEDb200U and PEDb300U, respectively. The ratio of an impulsive torque for PEDb300U to one for PEDb200U T_<imp300>/T_<imp200> is 0.8, which is quite different from the previous result 1.58. In the previous discussion, a contact time △t at an impulse moment was assumed to be the same for both driver mechanics. But they have their proper moment of inertia. The driver mechanics with a smaller momentum of inertia is easy to be rebounded, and has a shorter contact time at screw seating. This consideration suggests that a contact time △t for PEDb200U is a half of one for PEDb300U.
帝京平成大学の論文
2002-12-25