Half thrust bearing

A half thrust bearing for receiving an axial force of a crankshaft of an internal combustion engine, the half thrust bearing having a semi-annular shape and comprising a sliding surface for receiving the axial force, and a rear surface on an opposite side of the sliding surface, and the half thrust bearing defining a reference plane on a rear surface side that is perpendicular to an axial direction, wherein

• the sliding surface includes a flat surface portion extending in parallel with the reference plane from a radially inner end of the half thrust bearing to a radially outer end thereof, and inclined surface portions formed on both sides in a circumferential direction of the flat surface portion,
• an axial distance between the reference plane and the sliding surface is maximum in the flat surface portion,
• at any radial positions, the axial distance in the inclined surface portions is maximum at circumferential ends of the inclined surface portions on a circumferentially central portion side of the half thrust bearing and is reduced toward both circumferential end portions of the half thrust bearing,
• at any circumferential positions, the axial distance in the inclined surface portions is constant over a radial direction of the half thrust bearing, or maximum at the radially inner end of the half thrust bearing and is reduced toward the radially outer end, and
• the flat surface portion has a circumferential length extending over a circumferential angle of 5° or more and 35° or less, at any radial positions of the half thrust bearing.