What are the three types of transmission methods for camshafts?

Cylindrical gear transmission:
The upper and lower camshafts are mostly driven by cylindrical timing gears, with the crankshaft gear meshing with the camshaft gear through the intermediate gear. Timing gears often use helical teeth to ensure smooth meshing and reduce noise. Gears are made of steel or cast iron. Simple structure, convenient disassembly and assembly, and reliable process.
Bevel gear transmission:
It is mainly used for the transmission of overhead cams in lightweight, high-speed, and high-power internal combustion engines. The camshaft is far away from the crankshaft and is driven by bevel gears and vertical elastic shafts. Compact and reliable structure, but inconvenient disassembly and assembly.
Chain drive:
Chain transmission is often used on upper mounted camshaft air valve mechanisms, which can protect the air valve mechanism from inertial loads. This type of device requires high quality of the chain, and the chain should have a certain tension during operation. It is equipped with a locking sprocket, and adjusting the position of the locking sprocket can change the tension of the chain. The work reliability is good, but the durability is not as good as that of gear transmission devices.