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 two inclined flat 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 each inclined flat surface portion is maximum at a circumferential end of the inclined flat surface portion on a circumferentially central portion side of the half thrust bearing and is reduced toward a circumferential end portion of the half thrust bearing,
• each inclined flat surface portion is arranged to form one constant thickness portion which extends linearly from the radially inner end to the radially outer end of the half thrust bearing in an area between circumferential angles of 35° and 55° from the circumferential end portion toward the circumferentially central portion side of the half thrust bearing, the axial distance being constant in the constant thickness portion,
• at any circumferential positions, the axial distance in each inclined flat surface portion is maximum at the radially inner end and is reduced toward the radially outer end in a region of the inclined flat surface portion on a circumferential end portion side of the constant thickness portion, and is minimum at the radially inner end and is increased toward the radially outer end in a region of the inclined flat surface portion on the circumferentially central portion side of the constant thickness portion, 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.