Patent ID: 8631579

Claim:
A method for manufacturing an injection hole member formed with a taper hole, which serves as at least a part of an injection hole, the taper hole being formed so that a central axis of the taper hole is inclined with respect to an axis of a base material of the injection hole member in a thickness direction of the base material and a diameter of the taper hole increases in a direction from an end surface of the base material to an other end surface of the base material, the method comprising the steps of: forming a lead hole in the base material through punch press with a punch, the lead hole being formed so that a central axis of the lead hole is inclined with respect to the axis of the base material in the thickness direction thereof and a diameter of the lead hole is substantially constant along an extending direction of the central axis of the lead hole; and forming a taper hole in the base material by widening the lead hole with a taper punch, whose tip end is inserted into the lead hole in a state where a central axis of the taper punch is inclined to the same side as the central axis of the lead hole with respect to the axis of the base material in the thickness direction thereof, the taper punch being formed so that a diameter of the taper punch decreases toward the tip end thereof, wherein the injection hole member is formed so that an intersection line between a first reference plane, which is a virtual plane perpendicular to the central axis of the lead hole, and an inner peripheral surface of the lead hole is in an elliptic shape or a oval shape, whose major axis is directed in an extending direction of a reference axis, which is an intersection line between the first reference plane and a virtual plane including the central axis of the lead hole and the axis of the base material in the thickness direction thereof, and the injection hole member is formed so that an intersection line between a second reference plane, which is perpendicular to the central axis of the taper punch, and an outer peripheral surface of the taper punch is round in shape.