Patent ID: 8733198

Claim:
A helical gear including a hub mounted on a rotation shaft, a disk extending from said hub towards an outer side in a radial direction of said rotation shaft, and a rim provided at an outer side of said disk, said rim including a plurality of teeth at an outer peripheral face, said disk including a plurality of opening perimeter walls defining through holes provided along a perimeter of said hub, said opening perimeter wall including: an inner peripheral side face located at said hub side, an outer peripheral side face located at a side closer to said rim than said inner peripheral side face, a first end side face joining one end of said inner peripheral side face and one end of said outer peripheral side face, a second end side face joining the other end of said inner peripheral side face and the outer end of said outer peripheral side face, said outer peripheral side face including a first side region and a second side region located at a tail end side in direction of rotation of said helical gear relative to said first side region, as to a distance in said radial direction of said rotation shaft from said rim at said hub side to said outer peripheral side face, said first side region having the distance set greatest at the most leading end side spot in the direction of rotation of said helical gear, said first side region and said second side region provided continuously through an intersection, and a thickness of said disk gradually becoming thinner when viewed along the direction of rotation of said through hole from an end of said through hole towards said interconnection.