1. Gear drive
The valve mechanisms of the upper camshaft and the lower camshaft are mostly driven by cylindrical timing gears, and the crankshaft gears mesh with the camshaft gears through the intermediate gears.
The timing gears use helical teeth to ensure smooth meshing and reduce noise.
Gears are made of steel or cast iron.
Advantages: simple structure and process, convenient disassembly and assembly, and reliable process.
However, when the upper-mounted camshaft is geared, there are many intermediate gears, which increases the complexity and weight.
2. Bevel gear drive
This transmission method is mostly used for the transmission of overhead cams of light-duty high-speed and high-power internal combustion engines. Because the camshaft is far away from the crankshaft, bevel gears and vertical elastic shafts are used for transmission.
Its characteristics are: the structure is compact and reliable, but it is very complicated, and it is inconvenient to disassemble and assemble.
3. Chain drive
The chain drive is used on some upper camshaft valve mechanisms, which can protect the valve mechanism from inertial loads. This device requires high quality of the chain, and the chain should have a certain tension during operation to avoid de-chaining. Therefore, it is equipped with a slack stop sprocket, and the tension of the chain can be changed by adjusting the position of the slack stop sprocket. Its characteristics are: good working reliability, but less resistant than gear transmission.
