The camshaft of the lower mounted valve mechanism is located inside the crankcase, the camshaft of the middle mounted valve mechanism is located on the upper part of the engine body, and the camshaft of the upper mounted valve mechanism is located on the cylinder head. Most mass-produced cars now have engines equipped with overhead camshafts.More relevant information is as follows:
1. The layout of the camshaft: The common transmission methods between the camshaft and the crankshaft include gear transmission, chain transmission, and toothed belt transmission. The transmission between the lower and middle camshafts and the crankshaft mostly adopts cylindrical timing gear transmission. Generally, only a pair of gears are needed for transmission from the crankshaft to the camshaft. If the diameter of the transmission gear is too large, an additional intermediate idler gear can be added. In order to achieve smooth meshing and reduce working noise, most timing gears use helical gears.
2. Chain drive: Chain drive is commonly found between the overhead camshaft and crankshaft, but its reliability and durability are not as good as gear drive. Toothed tape is widely used instead of transmission chains in high-speed engines, but chain transmission is still used in some high-power engines. Toothed tape has the characteristics of low working noise, reliable operation, and low cost. For double overhead camshafts, the exhaust camshaft is generally driven by the crankshaft through timing toothed tape or chain, the intake camshaft is driven by the exhaust camshaft through metal chain, or both the intake and exhaust camshafts are driven by the crankshaft through toothed tape or chain.
