Common transmission modes between camshaft and crankshaft include gear transmission, chain transmission and toothed belt transmission. The transmission between the lower camshaft and the middle camshaft and the crankshaft is mostly driven by cylindrical timing gears. Generally, only a pair of gears is required from the crankshaft to the camshaft. If the diameter of the transmission gear is too large, an additional intermediate can be added Idler. In order to mesh smoothly and reduce working noise, most timing gears use helical gears.
Chain transmission is common between overhead camshaft and crankshaft, but its working reliability and durability are not as good as gear transmission. Toothed belts are widely used instead of transmission chains on high-speed engines, but chain transmission is still used on some high-power engines. Toothed tape has the characteristics of low working noise, reliable working and low cost. For dual overhead camshafts, generally the exhaust camshaft is driven by the crankshaft through a timing belt or chain, and the intake camshaft is driven by the exhaust camshaft through a metal chain, or both the intake camshaft and the exhaust camshaft Driven by the crankshaft through toothed tape or chain.