Ball bearing

A ball bearing comprising an outer ring having on its inner periphery an outer raceway, an inner ring having on its outer periphery an inner raceway, plural balls rotatably disposed between said outer raceway and said inner raceway, a cage holding said plural balls in a freely rotatable manner, and a grease packed in a space between said outer raceway and said inner raceway, wherein said grease comprises a base oil comprising a lubricant having a polar group in its molecular structure and a non-polar lubricant and a metallic soap-based thickener containing a long fibrous material whose fiber length is at least 3 μm in an amount of at least 30% by mass based on the total amount of the thickener;

• the inner peripheral surface of each pocket of the cage comprises a spherical part consisting of a spherical concave surface whose radius of curvature is slightly larger than that of each ball and a curved part which has the radius of curvature being larger than that of the spherical part and is smoothly continuous from the end of the spherical part toward the end thereof on the opening side of the pocket;
• and the radius of curvature of the cross-sectional shape of said inner raceway is in the range from 50.5% to 56.0% of the diameter of each ball, and the radius of curvature of the cross-sectional shape of said outer raceway is in the range from 53.0% to 58.0% of the diameter of each ball.

A ball bearing comprising an outer ring having on its inner periphery an outer raceway, an inner ring having on its outer periphery an inner raceway, plural balls rotatably disposed between said outer raceway and said inner raceway, a cage holding said plural balls in a freely rotatable manner, and a grease packed in a space between said outer raceway and said inner raceway, wherein said grease comprises a base oil comprising a lubricant having a polar group in its molecular structure and a non-polar lubricant, and a metallic soap-based thickener containing a long fibrous material whose fiber length is at least 3 μm in an amount of at least 30% by mass based on the total amount of the thickener;

• the cage is in the shape of circular ring as a whole and comprises pockets for receiving and holding the respective balls with its pocket surface at plural places in its circumferential direction and an opening whose width is smaller than the diameter of the ball on one side of the axial direction of each pocket, while a ratio δ/Da of an axial clearance δ provided between the rolling surface of the ball in the axial direction and the pocket surface to the diameter Da of each ball is set in a range from −0.01 to 0.02;
• and the radius of curvature of the cross-sectional shape of said inner raceway and the radius of curvature of the cross-sectional shape of said outer raceway are in the range from 51.0% to smaller than 60.0% of the diameter of each ball.

A ball bearing comprising an outer ring having on its inner periphery an outer raceway, an inner ring having on its outer periphery an inner raceway, plural balls rotatably disposed between said outer raceway and said inner raceway, a cage holding said plural balls in a freely rotatable manner, and a grease packed in a space between said outer raceway and said inner raceway, wherein said grease comprises a base oil, and a metallic soap-based thickener containing a fibrous material whose fiber length is at least 3 μm in an amount smaller than 30% by mass based on the total amount of the thickener;

• the cage is in the shape of circular ring as a whole and comprises pockets for receiving and holding the respective balls with its pocket surface at plural places in its circumferential direction and an opening whose width is smaller than the diameter of the ball on one side of the axial direction of each pocket, while a ratio δ/Da of an axial clearance δ provided between the rolling surface of the ball in the axial direction and the pocket surface to the diameter Da of each ball is set in a range from −0.01 to 0.02;
• and the radius of curvature of the cross-sectional shape of said inner raceway is in the range from 51.5% to 56.0% of the diameter of each ball and the radius of curvature of the cross-sectional shape of said outer raceway is in the range from 52.5% to 58.0% of the diameter of each ball.