A ball bearing not allowing locations where the surface pressure becomes locally higher at a race at the time of a high load and thereby keeping cracking from occurring and in turn realizing a longer lifespan is provided. A pair of races (12, 14) and at least one rolling element (16) movably clamped between the pair of races move are provided. A cross-sectional profile line (14a) of a part of each of the pair of races contacting the rolling element has the smallest radius of curvature at a position (P) sticking out the most in the first direction (D1) over which the pair of races face. The cross-sectional profile line becomes larger in radius of curvature the further from the position (P) in a second direction (D2) vertical to the first direction (D1) in the cross-section. The cross-sectional profile line is comprised of a single function. When a midpoint of the profile line in the second direction is the origin, an axis extending in the second direction is the X-axis and the axis extending in the first direction is the Y-axis, and a radius of the rolling element is (R), the cross-sectional profile line satisfies equation (1):
X.sup.2/{2R(1+0.05)}<Y<X.sup.2/{2R(10.05)}(1)

A retainer of a tapered roller bearing includes crossbars having guide surfaces which circumferentially contact the tapered rollers. The crossbars are also formed with first recessed surfaces and second recessed surfaces which are both in the form of cutouts circumferentially recessed from the respective guide surfaces to reduce stirring resistance and shear resistance of oil. To reduce the contact lengths between the rolling surface central portions of the tapered rollers and the guide surfaces, the guide surfaces are smoothly convex in the longitudinal direction of the tapered rollers.

A planetary gearing includes a sun gear rotating about a rotation axis and driven by a sun shaft; planet gears driven by the sun gear, each planet gear having an axially forward face side and an axially rearward face side; a ring gear engaging the planet gears; and planet slide bearing pins, wherein respectively one planet slide bearing pin is arranged inside a planet gear forming a lubricated journal bearing. At an axially forward face side and/or axially rearward face side, each planet gear forms a recess that extends inside the planet gear starting from the face side, and the planet slide bearing pins respectively form one crowning at their abutment surface such that their outer diameter decreases from a maximum outer diameter to at least an axial end of the abutment surface and has a minimum at the axial end.

A linear motion guide unit prevents damage to a corner portion of an end surface of a carriage resulting from high-speed rolling of the rolling elements, and eliminates the need for strict dimensional management of facing end surfaces of the carriage and a spacer. A crowning is formed at an end portion of the carriage, and an R chamfered portion is formed at a corner of an end surface of the carriage. An R chamfered portion is formed at a corner of the end surface of the spacer. The R chamfered portions define a valley portion between the facing surfaces of the carriage and the spacer. The rolling elements roll above the valley portion while striding it to thereby be prevented from colliding against the corner portion of the end surface of the carriage, whereby damage to the corner portion of the end surface of the carriage can be prevented.

A raceway surface (3a) of an outer ring (3) of a tapered roller bearing (1) includes a composite crowning surface. The composite crowning surface includes a center curve (3a1), which is formed at a center portion in a generating-line direction, and end portion curves (3a2 and 3a3), which are formed on both sides of the center curve (3a1) in the generating-line direction. The raceway surface (3a) of the outer ring (3) is entirely subjected to superfinishing. Each of a ratio (R.sub.2/R.sub.1) of a curvature radius (R.sub.2) of the end portion curve (3a2) to a curvature radius (R.sub.1) of the center curve (3a1) and a ratio (R.sub.3/R.sub.1) of a curvature radius (R.sub.3) of the end portion curve (3a3) to the curvature radius (R.sub.1) is set to 0.02 or more. Each of drop amounts of the end portion curves (3a2 and 3a3) is set to 0.07 mm or less.

A bushing may include a support surface and a sliding surface having a perimeter midpoint. The sliding surface of the bushing may have a convex profile in relation to a cross section of the bushing. The convex profile may be offset from the perimeter midpoint of the sliding surface of the bushing.

A bearing ring includes a raceway surface on which a roller of a roller bearing rolls, a rib portion end face that is provided on one side of the raceway surface in an axial direction and that faces a roller end face of the roller in which at least an outer circumferential side of the roller end face is a convex curved surface portion, and a recessed portion having a recessed shape provided in a corner between the raceway surface and the rib portion end face. The rib portion end face includes a contacting surface portion that the roller end face contacts, and a concave curved surface portion that is provided between the contacting surface portion and the recessed portion and that is smoothly continuous with the contacting surface portion. A curvature radius of the concave curved surface portion is greater than that of the convex curved surface portion.

A connecting rod for an internal combustion engine may include a big end passage for receiving a pin journal of a crankshaft, a small end passage for receiving a piston pin, and a beam extending between the big and small end passages. The small end passage may extend along a passage axis and be delimited by opposed edges. The small end passage may include an inner passage surface with a cylindrical surface portion having a first diameter. The small end passage may extend along the passage axis between the opposed edges. The inner passage surface may comprise profiled regions adjacent to the opposed edges and extending at least over a part of a circumference of the opposed edges. The profiled regions may begin from the cylindrical surface portion and increase into a maximum second diameter at the opposed edges. Further, a plurality of dimples may be positioned along the cylindrical surface portion of the inner passage surface.

A cam follower assembly includes a ball bearing having an outer ring and an inner assembly which includes two or more segments. The inner assembly is disposed in the outer ring with a full complement of balls disposed therebetween. The outer ring and inner assembly each include a race having a gothic arch cross sectional configuration that causes the balls to roll on two portions of each race.

A planetary roller bearing is disclosed. The planetary roller bearing includes an outer ring including a first set of teeth, an inner ring including a second set of teeth, and planetary rolling elements arranged between the outer ring and the inner ring. The planetary rolling elements each include a third set of teeth configured to engage with the first set of teeth and the second set of teeth. A height of at least three successive teeth gradually increases from an axial end of a selected set of the first, second, or third sets of teeth.