PROBLEM TO BE SOLVED: To provide a double helical gear capable of reducing gear noise by moving a resonance frequency to a low frequency side or reducing vibration, with a simple structure.SOLUTION: At an outer peripheral part between a first gear piece 2 and a second gear piece 3, formed is a projection part 7 integrated with the first gear piece 2 and the second gear piece 3 in an axial direction, and at the same position as the projection part 7 in a radial direction, a groove part 8 is formed with an interval in the axial direction with respect to the first gear piece 2 and the second gear piece 3. The groove part 8 is positioned on the opposite side to the projection part 7 with a rotation center axis as a center.SELECTED DRAWING: Figure 1
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