Wave generator of strain wave gearing

A wave generator of a strain wave gearing for flexing a flexible externally toothed gear into an ellipsoidal shape to partially mesh with a rigid internally toothed gear, and for moving meshing positions of the two gears in a circumferential direction;

• the wave generator comprising:
• a rigid plug having an ellipsoidal shape and a needle roller bearing mounted on an ellipsoidal plug external peripheral surface of the rigid plug, wherein
• the needle roller bearing has an ellipsoidal inner ring trajectory surface formed in the plug external peripheral surface, an outer ring capable of flexing in a radial direction, an outer ring trajectory surface formed in an inner peripheral surface of the outer ring, and a plurality of needle rollers mounted in a rollable state between the inner ring trajectory surface and the outer ring trajectory surface;
• an inner ring trajectory groove is formed in the plug external peripheral surface and extends in a circumferential direction of the plug external peripheral surface;
• the inner ring trajectory surface is formed in a groove bottom surface of the inner ring trajectory groove;
• and
• an inner-ring-side restricting surface for restricting the needle rollers from moving in an axis direction thereof is formed in groove side surfaces on both sides of the inner ring trajectory groove;
• and
• an outer ring trajectory groove is formed in an inner peripheral surface of the outer ring and extends in a circumferential direction of the inner peripheral surface;
• the outer ring trajectory surface is formed in a groove bottom surface of the outer ring trajectory groove;
• and,
• outer-ring-side restricting surfaces for restricting the needle rollers from moving in the axis direction thereof are formed on groove side surfaces on both sides of the outer ring trajectory groove.