Half bearing and sliding bearing

A half bearing for constituting a sliding bearing for supporting a crankshaft of an internal combustion engine, the half bearing having a semi-cylindrical shape and having an inner surface, the inner surface forming a sliding surface,

• wherein the sliding surface of the half bearing comprises a center zone and end zones on both sides of the center zone, the center zone including a circumferential center of the half bearing,
• wherein the sliding surface in each of the center zone and the end zones has a circular arc surface shape, a circle center of a circular arc surface of each of the end zones deviating from a circle center of a circular arc surface of the center zone away from the half bearing, the center zone being in a circumferential angle range of ±65° at maximum with respect to the circumferential center,
• wherein the center zone and the end zones each comprises a plurality of recesses, each recess having a recess surface and a peripheral edge, the recess surface being recessed from the sliding surface toward an outer diameter side of the half bearing,
• wherein the recess surface forms a convex curve toward the outer diameter side of the half bearing in cross-sectional view in a direction parallel to a circumferential direction of the half bearing,
• wherein the recess comprises a groove forming zone adjacent to the peripheral edge of the recess, the groove forming zone comprising a plurality of circumferential grooves, the circumferential grooves being recessed from the recess surface toward the outer diameter side of the half bearing,
• wherein the circumferential grooves extend from the peripheral edge of the recess along the circumferential direction of the half bearing,
• wherein an area ratio S2 of an area of the groove forming zone in the recess to an area of the recess in the end zone is larger than an area ratio of an area of the groove forming zone in the recess to an area of the recess in the center zone, and
• wherein a maximum depth D4 of the circumferential groove in the recess in the end zone is larger than a maximum depth D2 of the circumferential groove in the recess in the center zone.