Abstract: A method for manufacturing a coupling body includes a press-fitting step of press-fitting a coupling shaft-shaped portion of a valve member into a pit portion of a cap. A peripheral surface of a high-hardness component having a relatively high hardness of an outer peripheral surface of the coupling shaft-shaped portion of the valve member and an inner peripheral surface of the pit portion of the cap includes: a first-stage cylindrical surface having a diameter difference with respect to a peripheral surface of a low-hardness component; and a second-stage cylindrical surface positioned closer to a rear side in a press-fitting direction than the first-stage cylindrical outer peripheral surface and protruding in a radial direction to form a step with respect to the first-stage cylindrical surface.

Abstract: Provided is a prestroke adjustment method for a fuel injection valve capable of reducing variations in a prestroke amount regardless of the level of machining accuracy of a component. The prestroke adjustment method adjusts a prestroke amount D2 of a fuel injection valve 1 including a gap forming member 50 that forms a gap G2 defining a prestroke between a valve member 30 and engagement portions 33a and 423a of a movable core 42 by a second portion 52a abutting on the movable core 42 in a state where a first portion 51a is positioned at a reference position 33b of the valve member 30. In the prestroke adjustment method, a load L in the direction from the first portion 51a toward the reference position 33b of the valve member 30 is applied to the gap forming member 50 assembled to the valve member 30 to plastically deform the gap forming member 50, thereby shortening the relative length between the first portion 51a and the second portion 52a and setting the prestroke amount D2 to the target value T2.

Abstract: An object of the present invention is to provide a working method of an orifice, which has excellent working accuracy and high productivity in order to work an inclination portion (tapered portion) on the entire circumference of an inner wall of an orifice. Therefore, a working method of an orifice includes a first step of forming an orifice hole 54d in an orifice forming member, a second step of pressing a downstream end surface of the orifice forming member in which the orifice hole 54d opens, in a direction toward an upstream side of the orifice hole 54d by a punch 46 having a cutting blade portion 46a larger than a cross section of the orifice hole 54d. The second step causes a material of the orifice forming member to flow from an entire circumference at the downstream end portion of the orifice hole 54d to an inside of the orifice hole 54d to form a cross-sectional area reduction portion 54s in which a cross-sectional area of the orifice hole 54d is reduced from an upstream side to a downstream side.