Double helical gear and method of welding double helical gear

A method of welding a double helical gear including a rotating shaft, a first gear, and a second gear, the first gear and the second gear being disposed side by side in an axial direction on the rotating shaft, the first gear including a first teeth part at an outer peripheral part of the first gear, the second gear including a second teeth part at an outer peripheral part of the second gear, the first teeth part of the first gear and the second teeth part of the second gear being inclined in mutually opposite directions with respect to the axial direction, the first gear including a first annular part to be fitted to the rotating shaft at an inner peripheral part of the first gear, the first annular part including two end surfaces of a first end surface and a second end surface in the axial direction, and the second end surface being closer to the second gear than the first end surface is, the method comprising:

• forming a first weld zone on the first end surface by welding of the first end surface of the first annular part from the axial direction, the first weld zone having a welded part extending over a fitting portion between the inner peripheral part of the first annular part and the rotating shaft as the first end surface is seen from the axial direction;
• and
• forming a second weld zone that is located on the second end surface of the first annular part at a gap between the first teeth part of the first gear and the second teeth part of the second gear in the axial direction by welding the rotating shaft from a radially outer side.