Abstract: Both outer-side inner ring elements 14 apply preload to respective tapered rollers 16 by being pressed from both sides in an axial direction by an outwardly-directed, flange-like collar 30, formed on an outer circumferential surface of one end among both ends in the axial direction of an inner-side outer ring member 22, and by a holding ring 31, mounted on the other end of the inner-side outer ring member 22, or by a pair of holding rings 31, mounted on both ends in the axial direction of the inner-side outer ring member 22. A double row tapered roller bearing unit having good assembly precision, being easy to process, and enabling preload control and preload readjustment to be performed with ease is thereby provided.

Abstract: Both outer-side inner ring elements 14 apply preload to respective tapered rollers 16 by being pressed from both sides in an axial direction by an outwardly-directed, flange-like collar 30, formed on an outer circumferential surface of one end among both ends in the axial direction of an inner-side outer ring member 22, and by a holding ring 31, mounted on the other end of the inner-side outer ring member 22, or by a pair of holding rings 31, mounted on both ends in the axial direction of the inner-side outer ring member 22. A double row tapered roller bearing unit having good assembly precision, being easy to process, and enabling preload control and preload readjustment to be performed with ease is thereby provided.

Abstract: Problems to be solved by the present invention are to suppress increase in friction torque in an operation under an applied preload thereby suppressing heat generation and wear of a bearing, and to realize a low-noise and low-vibration operation at a high-speed rotation in addition to enhancement of a bearing life. Let d designate the diameter d of the ball (17) in a four-point contact ball bearing (11). Let Dp denote the diameter of a pitch circle of plural balls (17) disposed between both raceway surfaces (13a, 15a). Let L1 designate an inter-ball distance between the adjacent balls (17) on the pitch circle having the diameter Dp. Let r denote a curvature radius of each of grooves serving as raceway surfaces (13a, 15a), which circumscribe the ball (17) on the outer and inner races (13, 15), respectively. Let ? designates a contact angle between the ball (17) and each of the raceway surfaces (132a, 15a).