Abstract: A high-pressure piping part includes a body structure forged in a closed space. The body structure is formed to include a main body portion formed by forward extrusion and side arm portions formed by side extrusion. The main body portion has therein a fiber flow formed along a passage, and the side arm portion has therein a fiber flow formed along the passage. Therefore, the direction in which stress is applied to the passage of the body structure by an internal pressure is approximately perpendicular to the directions of the fiber flows, thereby improving the degree of allowance of the resistance to pressure of the body structure for an injector.

Abstract: In a method of manufacturing a center electrode for a spark plug, a core member is press-fitted into a metal cup and, thereafter, a cold-forging process is performed to form a small-diameter portion at a closed end of the metal cup. The small-diameter portion is completely free from deformation which may occur during press-fitting operation. Thus, the small-diameter portion has excellent accuracy in shape. Furthermore, since the press-fitting is performed before the cold-forging of the small-diameter portion, it is possible to increase the press-fitting load or pressure to the extent that the core member and the metal cup are joined together with a sufficient degree of adhesion which will insure the a center electrode to have good thermal conductivity.

Abstract: A high-pressure piping part includes a body structure forged in a closed space. The body structure is formed to include a main body portion formed by forward extrusion and side arm portions formed by side extrusion. The main body portion has therein a fiber flow formed along a passage, and the side arm portion has therein a fiber flow formed along the passage. Therefore, the direction in which stress is applied to the passage of the body structure by an internal pressure is approximately perpendicular to the directions of the fiber flows, thereby improving the degree of allowance of the resistance to pressure of the body structure for an injector.

Abstract: In a method of manufacturing a center electrode for a spark plug, a core member is press-fitted into a metal cup and, thereafter, a cold-forging process is performed to form a small-diameter portion at a closed end of the metal cup. The small-diameter portion is completely free from deformation which may occur during press-fitting operation. Thus, the small-diameter portion has excellent accuracy in shape. Furthermore, since the press-fitting is performed before the cold-forging of the small-diameter portion, it is possible to increase the press-fitting load or pressure to the extent that the core member and the metal cup are joined together with a sufficient degree of adhesion which will insure the a center electrode to have good thermal conductivity.