Half bearing and sliding bearing

A half bearing constituting a sliding bearing that supports a crankshaft of an internal combustion engine, the half bearing having a semi-cylindrical shape and including an inner circumferential surface and an outer circumferential surface, the half bearing comprising:

• at least one protrusion, the protrusion projecting outward in a radial direction from the outer circumferential surface,
• wherein a recessed portion recessed inward in the radial direction from the outer circumferential surface is formed over an entire circumferential-direction length between the protrusion and a circumferential-direction end surface of the half bearing,
• the protrusion is located between both end surfaces of the half bearing in an axial direction,
• the recessed portion includes a recessed portion bottom surface that is parallel with the axial direction of the half bearing when seen in a section that is parallel with the circumferential-direction end surface, two recessed portion side surfaces that perpendicularly intersect the axial direction of the half bearing at both ends of the recessed portion in the axial direction of the half bearing, and two recessed portion curved surfaces that connect the recessed portion side surfaces to the recessed portion bottom surface,
• two radial-direction grooves are formed in the circumferential-direction end surface of the half bearing relative to the protrusion, each of the two radial-direction grooves being adjacent to each of the recessed portion side surfaces,
• an extension length of the radial-direction grooves is greater than a depth of the recessed portion,
• the radial-direction grooves extend in the radial direction along the recessed portion side surfaces from the outer circumferential surface toward the inner circumferential surface of the half bearing, the radial-direction grooves being separated from the recessed portion at a midpoint of the extension,
• an inner circumferential surface-side end portion in an extending direction of the radial-direction grooves is located between the recessed portion bottom surface and the inner circumferential surface of the half bearing, and
• a groove width and a groove depth of the radial-direction grooves decrease from the position separated from the recessed portion toward the inner circumferential surface-side end portion and reach zero at the inner circumferential surface-side end portion.