Roller chain transmission device

A roller chain transmission in the timing draive of an automobile engine, the transmission comprising a toothed driving sprocket on a crankshaft of the engine, at least one toothed driven sprocket on a camshaft of the engine, and a roller chain having interleaved pairs of inner and outer plates, cylindrical bushings fixed to bushing holes in the inner plates, pins rotatable in said bushings and fixed to pin holes in the outer plates, rollers rotatable on said bushings, said toothed sprockegts meshing with the roller chain,

• wherein the outer diameter D of the rollers, the outer diameter d of the pins and the height H of the inner plates satisfy the following relationships with respect to the pitch P of the roller chain:
• 0.72P≦D≦0.79P
• 0.40P≦d≦0.44P
• 0.96P≦H
• and
• wherein the teeth of at least one of said sprockets have an arc-shaped tooth gap bottom having a radius R1, an asymmetric shape on the chain entering side and the chain leaving side with respect to a tooth center line, and, if the chain entering side tooth flank radius is defined as R2, and the radius of an arc of the chain entering side of the tooth head portion is defined as R3, the sprocket satisfies the following relationships:
• 0.505D≦R1≦0.505D+0.069D
• P−(0.505D+0.069D)≦R2≦P−0.505D
• 0.08≦R3≦0.13P
• where R1, R2, R3, D, and P are measured in millimeters.