| 主权项 |
1. A flexible externally toothed gear for a wave gear device comprising:
a boss constituted by a disc- or ring-shaped rigid body; a diaphragm plate that is continuous with an outer circumferential part of the boss and extends outward in a radial direction of the boss; a cylindrical cup body, continuous with a round outer periphery part of the diaphragm plate, that extends in a direction of a central axis of the boss and is capable of flexing in a radial direction thereof; and external teeth formed on a part of an outer circumferential surface of the cylindrical cup body at a side of an open end of the cylindrical cup body; the diaphragm plate being inclined with respect to a perpendicular plane that is perpendicular to the central axis, the diaphragm plate being inclined in a direction such that an outer periphery part of the diaphragm plate moves away from the open end of the cylindrical cup body, from an inner periphery part of the diaphragm plate toward the outer periphery part of the diaphragm plate, the outer periphery part of the diaphragm plate being continuous with the cylindrical cup body, and the inner periphery part of the diaphragm plate being continuous with the outer circumferential part of the boss, wherein: an inner end surface of the diaphragm plate on a side of the open end is smoothly continuous with an inner end surface of the boss on a side of the open end, and an outer end surface of the diaphragm plate on an opposite side to the open end is smoothly continuous with a round outer circumferential surface of the boss, and wherein, and when bisected by a plane along the central axis, the inner end surface of the boss is defined by an inner straight line perpendicular to the central axis, the inner end surface of the diaphragm plate is defined by an inner convexly curved line that is smoothly continuous with an endpoint of the inner straight line and convexly curved inward, and an inner inclined straight line that is smoothly continuous with an endpoint of the inner convexly curved line, the inner inclined straight line is inclined at a first angle of inclination with respect to the inner straight line defining the inner end surface of the boss in a direction such that an endpoint thereof nearer the cylindrical CUP body moves away from the inner end surface of the boss with respect to the endpoint nearer the boss, an outer end surface of the boss on a side opposite the inner end surface of the boss is defined by an outer straight line that is perpendicular to the central axis, a round outer circumferential surface of the boss continuous with an outer periphery of the outer end surface of the boss is defined by an outer circumference straight line that bends back to extend from a endpoint of the outer straight line toward the inner end surface of the boss, the outer end surface of the diaphragm plate is defined by a concavely curved line that tis smoothly continuous with an endpoint of the outer circumference straight line and curves concavely inward, a second concavely curved line that is smoothly continuous with an endpoint of the first concavely curved line and curves concavely inward, a third concavely curved line that is smoothly continuous with an endpoint of the second concavely curved line, and an outer inclined straight line that is smoothly continuous with an endpoint of the third concavely curved line, the radii of curvature of the first concavely curved line, the second concavely curved line, and the third concavely curved line are set so as to increase in that order, and the outer inclined straight line is inclined at a second angle of inclination, smaller than the first angle of inclination, in a same direction as the inner inclined straight line. |
