A half thrust bearing having a semi-annular shape including a first circumferential end portion and a second circumferential end portion, the half thrust bearing comprising:
- a sliding surface configured to receive an axial force of a crankshaft;
- and
- a rear surface on an opposite side of the sliding surface, wherein the rear surface is parallel to a reference plane on a rear surface side, wherein the reference plane is perpendicular to an axial direction of the half thrust bearing, wherein
- the sliding surface includes:
- a flat surface portion extending, in parallel to the reference plane, from an inner circumference of the half thrust bearing to an outer circumference of the half thrust bearing,
- a first inclined flat surface portion formed at a first side of the flat surface portion in a circumferential direction of the half thrust bearing, and
- a second inclined flat surface portion formed at a second side of the flat surface portion in the circumferential direction of the half thrust bearing,
- an axial distance between the rear surface and the sliding surface is maximum in the flat surface portion,
- in the first inclined flat surface portion, the axial distance is maximum at a third circumferential end of the first inclined flat surface portion and decreases toward the first circumferential end portion of the half thrust bearing, wherein the third circumferential end is adjacent to the flat surface portion,
- in the second inclined flat surface portion, the axial distance is maximum at a fourth circumferential end of the second inclined flat surface portion, and decreases toward the second circumferential end portion of the half thrust bearing, wherein the fourth circumferential end is adjacent to the flat surface portion,
- the first inclined flat surface portion includes a first constant thickness portion which extends linearly from the inner circumference to the outer circumference, wherein the first constant thickness portion is located at a central angle in a range of 35° to 55° from the first circumferential end portion toward a circumferentially central portion of the half thrust bearing,
- the second inclined flat surface portion includes a second constant thickness portion which extends linearly from the inner circumference to the outer circumference, wherein the second constant thickness portion is located at a central angle in a range of 35° to 55° from the second circumferential end portion toward the circumferentially central portion of the half thrust bearing,
- in the circumferential direction, the axial distance is maximum at the inner circumference and decreases toward the outer circumference in a region between the first constant thickness portion and the first circumferential end portion of the half thrust bearing, and is minimum at the inner circumference and increases toward the outer circumference in a region between the first constant thickness portion and the first side of the flat surface portion,
- in the circumferential direction, the axial distance is maximum at the inner circumference and decreases toward the outer circumference in a region between the second constant thickness portion and the second circumferential end portion of the half thrust bearing, and is minimum at the inner circumference and increases toward the outer circumference in a region between the second constant thickness portion and the second side of the flat surface portion, and
- the flat surface portion has a circumferential length extending over a central angle of 5° or more and 35° or less, at any radial positions of the half thrust bearing.