Patent ID: 8381608

Claim:
A gear, wherein (1) a first curved surface smoothly connected to a tooth face of an involute tooth form and convex in a direction opposite to the tooth face, (2) a flat surface connected to the first curved surface, and (3) a second curved surface smoothly connected to the flat surface and convex in the same direction as the first curved surface are formed on a tooth root side of a tooth, the shape of the flat surface in a normal plane thereof is a tangent in contact with a tip side end of a trajectory of motion of a tooth of a meshing partner gear and intersecting with a tooth form center line at a 30° angle when an end of the flat surface on the first curved surface side is extended, the shape of the second curved surface in a normal plane thereof is a circular arc shape formed by a circular arc in contact with the tooth face and a root circle of the involute tooth form, and having a maximum curvature radius among circular arcs not interfering with the trajectory of motion of the tooth of the meshing partner gear, the circular arc being moved along a tooth space center line to a position in contact with the tangent, and the shape of the first curved surface in a normal plane thereof is a circular arc shape in contact with the tooth face and the tangent, and having a maximum curvature radius among circular arcs that do not interfere with the trajectory of motion of the tooth of the meshing partner gear.