A ball bearing unit for a turbocharger according to an embodiment includes: an outer ring, a first inner ring, a second inner ring, a first machined retainer and a second machined retainer. The outer ring has an inner peripheral surface provided with an outer ring raceway surface at one end side and an outer ring raceway surface at another end side. At least one of the first machined retainer and the second machined retainer includes a plurality of pockets that hold the plurality of balls in a rollable manner in a circumferential direction. Each of the pockets has a diameter of equal to or more than 1.03 times and equal to or less than 1.07 times of a diameter of the balls.

Provided is a tapered roller bearing of an inner ring guidance design. A smaller diameter annular part of a cage and a smaller rib of an inner ring of the bearing defines a smaller diameter-side clearance S.sub.1. A larger diameter annular part of the cage and a larger rib of the inner ring defines a larger diameter-side clearance S.sub.2. The bearing defines a dimensionless number Y which is in the range of at least 0.39 to no more than 0.88 according to the following equation: Y=(S.sub.max/S.sub.3)?(d/l) where d and l are a mean roller diameter and a roller length of the tapered rollers, respectively, S.sub.3 corresponds to the equation: S.sub.3=(W/2)/tan ??(PCD/2+(d/2)/sin ??((D/2).sup.2?(W/2).sup.2).sup.1/2), S.sub.max is chosen from the maximum values of S.sub.1 and S.sub.2, W is a pocket width of the cage, ? is a pillar angle which is a half of the angle formed, in a section corresponding to the mean roller diameter d, by surfaces of adjacent pillars of the cage that make contact with a tapered roller located in between, PCD is the diameter of roller centers representing the pitch circle diameter of the arrangement of the tapered rollers, and D is a cage inner diameter.

A tapered roller bearing includes: an inner ring including an inner raceway surface tapered so that the inner raceway surface increases in diameter from a first side to a second side; an outer ring including an outer raceway surface tapered so that the outer raceway surface increases in diameter from the first side to the second side; a plurality of tapered rollers disposed in an annular space defined between the inner ring and the outer ring; and an annular cage retaining the tapered rollers. The cage includes: a small diameter annular portion; a large diameter annular portion; and a plurality of cage bars connecting the small and large diameter annular portions. An outer clearance is defined between the outer ring and the cage and between circumferentially adjacent ones of the tapered rollers. The outer clearance has a cross-sectional area increasing from the second side to the first side.

A ball bearing unit for a turbocharger according to an embodiment includes: an outer ring, a first inner ring, a second inner ring, a first machined retainer and a second machined retainer. The outer ring has an inner peripheral surface provided with an outer ring raceway surface at one end side and an outer ring raceway surface at another end side. At least one of the first machined retainer and the second machined retainer includes a plurality of pockets that hold the plurality of balls in a rollable manner in a circumferential direction. Each of the pockets has a diameter of equal to or more than 1.03 times and equal to or less than 1.07 times of a diameter of the balls.

A tapered roller bearing includes: an inner ring including an inner raceway surface tapered so that the inner raceway surface increases in diameter from a first side to a second side; an outer ring including an outer raceway surface tapered so that the outer raceway surface increases in diameter from the first side to the second side; a plurality of tapered rollers disposed in an annular space defined between the inner ring and the outer ring; and an annular cage retaining the tapered rollers. The cage includes: a small diameter annular portion; a large diameter annular portion; and a plurality of cage bars connecting the small and large diameter annular portions. An outer clearance is defined between the outer ring and the cage and between circumferentially adjacent ones of the tapered rollers. The outer clearance has a cross-sectional area increasing from the second side to the first side.

A rolling-element bearing in which a rolling element is retained in each of retaining openings formed in a retainer and method for manufacturing the bearing are provided. Each retaining opening is defined by a pair of inner side faces facing each other, and a pair of inner end faces facing each other. In the manufacturing method, with a support die being brought into contact with one of the inner side faces and the inner end faces of one of the retaining openings, the outer and inner circumferential surfaces of the retainer are pressed by an outer punch and an inner punch. Accordingly, on at least one of the inner side faces and the inner end faces, a first retaining piece and a second retaining piece for preventing the rolling element from falling off are formed on the outer circumferential surface and the inner circumferential surface of the retainer, respectively.

The invention relates to a method for producing a rolling bearing cage for a rolling bearing comprising at least one row of rolling elements. In the method according to the invention, a ring or a ring element made of a metallic solid material is provided and shaped by a forming process and/or a cutting, material-removing process into an annular or segmented main body of the rolling bearing cage. The main body has openings for receiving a respective rolling element, the main body being heated to a temperature above a minimum coating temperature for thermal coating with a thermoplastic material powder, wherein the main body is then immersed in a fluidized bed containing the thermoplastic material powder, wherein thermoplastic material powder adheres to the main body, melts and forms a contiguous coating while the main body is present in the fluidized bed, and wherein, after the coating, the main body is removed from the fluidized bed. The invention further relates to an axial-radial rolling bearing with the described rolling bearing cage.

A bearing cage for large rolling-element bearings includes a first side part and a second side part and a plurality of bridge elements connecting the first and second side parts to form a plurality of cage pockets each configured to receive a rolling element. The at least one bridge element and/or the first side part and/or the second side part includes at least one opening, and an insert element is mounted in each of the at least one opening and configured to contact the rolling element.

A tapered roller bearing of an inner ring guidance design. A smaller diameter annular part of a cage and a smaller rib of an inner ring of the bearing defines a smaller diameter-side clearance S.sub.1. A larger diameter annular part of the cage and a larger rib of the inner ring defines a larger diameter-side clearance S.sub.2. The bearing defines a dimensionless number Y which is in the range of at least 0.39 to no more than 0.88 according to the following equation: Y=(S.sub.max/S.sub.3)(d/l) where d and l are a mean roller diameter and a roller length of the tapered rollers, respectively, S.sub.3 corresponds to the equation: S.sub.3=(W/2)/tan (PCD/2+(d/2)/sin ((D/2).sup.2(W/2).sup.2).sup.1/2), S.sub.max is chosen from the maximum values of S.sub.1 and S.sub.2, W is a pocket width of the cage, is a pillar angle which is a half of the angle formed, in a section corresponding to the mean roller diameter d, by surfaces of adjacent pillars of the cage that make contact with a tapered roller located in between, PCD is the diameter of roller centers representing the pitch circle diameter of the arrangement of the tapered rollers, and D is a cage inner diameter.

A holder for a self-aligning roller bearing, having a central annular part with lintels fixed on side surfaces thereof in an axial direction and protruding parts which protrude closer to the outer sides in a radial direction than the lintels. The holder includes reinforcement parts fixed to the central annular part and the lintels on outer sides of the lintels in the radial direction and on outer sides of the protruding parts in the axial direction. In cross sections cut out along the axial direction and radial direction, at least a part of a contour line of outer side surfaces of the reinforcement parts in the axial direction extends inwardly in the radial direction while extending toward outwardly in the axial direction. A self-aligning roller bearing having the holder with improved connection strength of connection parts between the lintels and the central annular part prolongs bearing service life.