Patent ID: 8250941

Claim:
A pair of gears, each of which has a tooth to be engaged with another mating tooth, wherein one tooth flank ( 4 a ) of one gear (W 1 a ) is designed using a CAD system by continuously transitioning a tooth trace consisting of a circular arc (R 1 ), from a tooth root of the gear to a tooth tip thereof, and a mating tooth flank ( 3 b ) of a mating gear (W 1 b ), which is to come in contact with the one tooth flank ( 4 a ), is designed using a CAD system by continuously transitioning a tooth trace curve (R 2 ) consisting of two circular arcs ( 61 , 63 ) and of a connecting curve ( 65 ) connecting the two circular arcs ( 61 , 63 ), from a tooth root of the mating gear to a tooth tip thereof, each circular arc ( 61 , 63 ) being formed by a circle ( 62 , 64 ), the circle ( 62 , 64 ) being generated, for each of two contact points at which a hypothetical tooth trace ( 54 ) contacts with a mating contact curve (R 4 ), in such a manner that the circle ( 62 , 64 ) comes in contact with a circular arc being the corresponding hypothetical tooth trace ( 54 ) and has a diameter smaller than that of the circular arc being the corresponding hypothetical tooth trace ( 54 ).