Curved groove ball bearing without retainer

A curved groove ball bearing without a retainer, comprising:

• an outer ring,
• a plurality of steel balls, and
• an inner ring;
• wherein:
• the outer ring and the inner ring respectively has a first curved groove and a second curved groove, the outer ring has a first wall and a second wall, the inner ring has a third wall and a fourth wall;
• wherein the first wall of the outer ring is thicker than the second wall of the outer ring, and the third wall of the inner ring is thicker than the fourth wall of the inner ring;
• a plurality of peaks and valleys are formed on the outer ring along a center line of the first curved groove and pendulate along an axis of the bearing, and a plurality of peaks and valleys respectively corresponding to the number of the plurality of peaks and valleys of the outer ring are formed on the inner ring;
• curved surfaces of the outer ring and the inner ring respectively contacting the steel balls are symmetrical with respect to a center line formed by centers of the steel balls;
• a thickness of the fourth wall of the inner ring is equal to or smaller than a radius of each of the steel balls;
• a thickness of the third wall of the inner ring is equal to or smaller than a diameter of respective steel balls;
• the second wall of the outer ring is tangent to an arc of the second curved groove;
• a distance between tops of adjacent peaks in an axial direction is larger than a sum of an amplitude of the inner ring in the axial direction and the diameter of each of the steel balls;
• and
• a thickness of the first wall of the outer ring is equal to or smaller than a minimum distance from a center of each of the steel balls to an outer circumferential surface of the outer ring;
• and a distance between bottoms of adjacent valleys is larger than the sum of the amplitude of the inner ring in the axial direction and the diameter of each of the steel balls.