Patent ID: 6517460
Filing Date: 2003-02-11
Classification: F16H

Abstract:
An eccentric orbiting speed reducer comprising:an internal tooth member having internal teeth formed on an inner circumference; a first rotational member with a plurality of circular grooves formed inside that is carried rotatably by said internal tooth member, while keeping a coaxial relation with said internal tooth member; a second rotational member with a plurality of circular grooves formed inside, said plurality of circular grooves being opposed respectively to said plurality of circular grooves for said first rotational member, said second rotational member being carried rotatably by said internal tooth member, while keeping a coaxial relation with said internal tooth member; an external gear having external teeth formed on an outer circumference, with a plurality of through holes formed inside, said external teeth meshing with said internal teeth of said internal tooth member, said external gear being carried between said first rotational member and said second rotational member; a plurality of crankshafts having first insertion portions to be inserted respectively into said plurality of pairs of opposed circular grooves for said first rotational member and said second rotational member, and second insertion portions to be inserted respectively into said plurality of through holes for said external gear and orbiting eccentrically said external gear, said crankshafts being arranged circumferentially with respect to an axis of said internal tooth member; a plurality of pairs of first bearings for holding said first insertion portions of said crankshafts rotatably with respect to said first rotational member and said second rotational member, respectively; and a plurality of second bearings for holding said second insertion portions of said crankshafts rotatably with respect to said external gear; wherein a basic radial load rating of said first bearing into which said first insertion portion of one of said plurality of crankshafts is inserted is greater than basic radial load ratings of said first bearings into which said first insertion portions of the remaining crankshafts among said plurality of crankshafts are inserted.