Wave generator and strain wave gearing

A wave generator of a strain wave gearing for flexing a flexible externally toothed gear elliptically to partially mesh with a rigid internally toothed gear and to move meshing portions of the gears in a circumferential direction, the wave generator comprising:

• a rigid plug, and a roller bearing that is fitted on an elliptical plug outer circumferential surface of the plug and is flexed elliptically,
• wherein the roller bearing has an inner ring, an outer ring, a plurality of rollers accommodated rollably in a raceway between the inner ring and the outer ring, a retainer for holding the rollers in the raceway at prescribed intervals in a circumferential direction, and flange plates fixed to or integrally formed in side parts on both sides of the plug in an axial line direction;
• each of the flange plates has an outer circumferential edge portion protruding outward from the plug outer circumferential surface and is located on both sides of the raceway in the axial line direction of the raceway;
• the rollers are arranged so that, when the rollers move in the axial line direction, the rollers come in engagement with the respective outer circumferential edge portions and movements of the rollers in the axial line direction are constrained;
• the retainer is arranged so that, when the retainer moves in the axial line direction, the retainer comes in engagement with the rollers and a movement of the retainer in the axial line direction is constrained;
• a profile shape of the outer circumferential edge portions of the flange plates is a circle or an ellipse;
• and
• the outer circumferential edge portions have a projecting height measured from an elliptical inner-ring-side raceway surface of the raceway, the projecting height having a dimension in a range of 15% to 40% of a diameter of the roller at a major-axis position of the elliptical inner-ring-side raceway surface.