Cutting insert, cutting tool, and method of manufacturing machined product

A cutting insert, comprising:

• a polygonal plate shape formed by an upper surface, a lower surface, a mounting hole extending from the lower surface to the upper surface, and a side surface located between the upper surface and the lower surface, and
• a cutting edge formed at an intersecting portion between the upper surface and the side surface, wherein
• the upper surface comprises a breaker groove located along the cutting edge, and a convex portion located closer to a mounting hole longitudinal axis than the breaker groove,
• the convex portion comprises a main portion which has a flat upper end surface, a first projecting portion which projects in a direction away from the main portion toward a corner portion of the upper surface, a second projecting portion which projects in a direction away from the first projecting portion toward the corner portion, and whose height from the lower surface is lower than an upper end of the first projecting portion, and a third projecting portion which projects in a direction away from the second projecting portion toward the corner portion, and whose height from the lower surface is lower than an upper end of the second projecting portion,
• the second projecting portion includes a height which is constant along a majority of a distance between the first projecting portion and the third projecting portion in a direction from the mounting hole longitudinal axis toward the corner portion,
• a first flat inclined wall surface located between the first projecting portion and the second projecting portion,
• a second wall surface located between the second projecting portion and the third projecting portion, wherein the second wall surface is a convex curved surface shape positioned apart from the first flat inclined wall surface, and
• a third wall surface located between a front end of the third projecting portion and the breaker groove, wherein the third wall surface is a convex curved surface shape,
• wherein the first projecting portion has a flat surface shape,
• the second projecting portion and the third projecting portion have upward convex curved surface shapes,
• the third wall surface is apart from the first flat inclined wall surface, and
• wherein the third projecting portion is apart from the first flat inclined wall surface.