The shaft coupling structure includes: a male joint, and a female shaft that is coupled to male joint. The outer peripheral surface of the male joint has an outer peripheral side concave-convex portion having a concave-convex shape in the circumferential direction and an annular concave groove, and the inner peripheral surface of the female shaft has an inner peripheral side concave-convex portion having a concave-convex shape in the circumferential direction. The outer peripheral side concave-convex portion and the inner peripheral side concave-convex portion engage with a concave-convex engagement. The outer peripheral surface of the male joint and an end portion on one side of the female shaft in the axial direction are welded and fixed together, and an embossed portion provided on the inner peripheral surface of the female shaft is arranged on the inner side of the annular concave groove.

The shaft coupling structure includes: a male joint, and a female shaft that is coupled to male joint. The outer peripheral surface of the male joint has an outer peripheral side concave-convex portion having a concave-convex shape in the circumferential direction and an annular concave groove, and the inner peripheral surface of the female shaft has an inner peripheral side concave-convex portion having a concave-convex shape in the circumferential direction. The outer peripheral side concave-convex portion and the inner peripheral side concave-convex portion engage with a concave-convex engagement. The outer peripheral surface of the male joint and an end portion on one side of the female shaft in the axial direction are welded and fixed together, and an embossed portion provided on the inner peripheral surface of the female shaft is arranged on the inner side of the annular concave groove.

An assembly and a method for manufacturing an assembly for transmitting torque to an aircraft actuator. The assembly and method include a torque tube having a longitudinal axis and an end fitting. The ending fitting includes a connector portion and an engagement portion that is inserted into the torque tube. The engagement portion includes a first end adjacent the connector portion, a second end opposite the first end, and a coupling region between the first and second end that includes an outer coupling surface having an outer diameter and a continuous groove formed thereon. The continuous groove includes two axial grooves that extend along the outer coupling surface along the longitudinal axis and a first parallel groove that extends circumferentially about the longitudinal axis along the outer coupling surface that joins the two axial grooves.

A heat treatment method is provided in which a first steel component (11) formed with a coating (111) thereon is fitted in first holes (123, 124) of a second steel component (12) subjected to a quenching treatment. The heat treatment method includes a heating step of heating the second steel component to a first temperature (T.sub.1) equal to or higher than a tempering temperature (T.sub.0) of the second steel component and higher than a temperature of the first steel component by a temperature difference (ΔT) for achieving shrink fitting and a shrink-fitting step of shrink-fitting the first steel component in the first holes of the second steel component in a state of maintaining the temperature difference for achieving shrink fitting between the first steel component and the second steel component.

A heat treatment method is provided in which a first steel component (11) formed with a coating (111) thereon is fitted in first holes (123, 124) of a second steel component (12) subjected to a quenching treatment. The heat treatment method includes a heating step of heating the second steel component to a first temperature (T.sub.1) equal to or higher than a tempering temperature (T.sub.0) of the second steel component and higher than a temperature of the first steel component by a temperature difference (ΔT) for achieving shrink fitting and a shrink-fitting step of shrink-fitting the first steel component in the first holes of the second steel component in a state of maintaining the temperature difference for achieving shrink fitting between the first steel component and the second steel component.

A method for manufacturing a torque-transmitting assembly includes: turning an inner component (b) machining an outermost surface of the inner component such that the outermost surface of the inner component has a continuous convex shape; (c) turning an external component; (d) machining an innermost surface of the external component such that the innermost surface of the external component has a continuous convex shape; (e) heating the innermost surface of the external component to expand a size of the innermost surface after machining the innermost surface of the external component; (f) placing the heated external component onto the inner component while the inner component is maintained at room temperature; and (g) holding the inner component and the external component in place until an interface between the innermost surface of the external component and the outermost surface of the inner component reaches the room temperature.

A method for manufacturing a torque-transmitting assembly includes: turning an inner component (b) machining an outermost surface of the inner component such that the outermost surface of the inner component has a continuous convex shape; (c) turning an external component; (d) machining an innermost surface of the external component such that the innermost surface of the external component has a continuous convex shape; (e) heating the innermost surface of the external component to expand a size of the innermost surface after machining the innermost surface of the external component; (f) placing the heated external component onto the inner component while the inner component is maintained at room temperature; and (g) holding the inner component and the external component in place until an interface between the innermost surface of the external component and the outermost surface of the inner component reaches the room temperature.

A forging method for a shaft member includes preforming at least one of a plurality of enlarged diameter portions to obtain a semi-finished member, and forming a remainder of the enlarged diameter portions in the semi-finished member using a mold. The mold includes a punch, split dies, and a workpiece receiving member. The forming of the remainder of the enlarged diameter portions includes allowing the semi-finished member having the at least one of the enlarged diameter portions to be placed on the workpiece receiving member, cramping the semi-finished member in its radial direction by closing the split dies, and filling the semi-finished member into forming surfaces of the split dies by the pressure applied by the punch under the state in which the semi-finished member is cramped.

A forging method for a shaft member includes preforming at least one of a plurality of enlarged diameter portions to obtain a semi-finished member, and forming a remainder of the enlarged diameter portions in the semi-finished member using a mold. The mold includes a punch, split dies, and a workpiece receiving member. The forming of the remainder of the enlarged diameter portions includes allowing the semi-finished member having the at least one of the enlarged diameter portions to be placed on the workpiece receiving member, cramping the semi-finished member in its radial direction by closing the split dies, and filling the semi-finished member into forming surfaces of the split dies by the pressure applied by the punch under the state in which the semi-finished member is cramped.

In one an exemplary aspect of the present disclosure, an engine includes a drive shaft; an electric machine including a stator assembly and a rotor assembly, the rotor assembly rotatable relative to the stator assembly; and an electrical break, the drive shaft coupled to the rotor assembly through the electrical break.