Patent attributes
Provided are a sprocket and a chain transmission mechanism configured such that noise and vibrations caused by the elongation of the chain and also wear of parts are reduced, the decrease in the meshing strength of the chain and the sprocket is inhibited, and the chain service life is extended. The sprocket and chain transmission mechanism each have bottom land portion arcs of a predetermined radius and a predetermined angular range between a plurality of teeth to be meshed with the chain. The radius of each of the bottom land portion arcs satisfies the following relationship with the diameter of a roller or a bush of the meshing chain: Rb>0.505*φr+0.069*φr1/3 (where Rb is the bottom land portion arc radius, and φr is the diameter of the roller or the bush of the meshing chain).
