The bottom-mounted camshaft usually uses a star-shaped […]
The bottom-mounted camshaft usually uses a star-shaped gear train (the so-called control wheel), and the roller chain or rack to be attached to the crankshaft. In order to control noise, drive wheels at the camshaft with large diameter are usually made of plastic or light metals, while that of relatively small diameter crankshaft are mostly made of steel.
Chain connection is also common. This method is available on the bottom and top camshafts. In order to reduce noise (usually the oscillation noise produced by the chain in motion), a hydraulic clamping device and a plastic material guide are usually attached.
One of the most common types of overhead camshaft structures is the connection of a plastic rack chainThe rack chain is located outside the engine oil chamber and is provided with a steel embedded component that helps to tighten through an adjustable roller.
There is another kind of structure, because the power consumption is too large and complicated in transmission, it is rare now. The structure is connected to an overhead camshaft and a crankshaft by an eccentric link, a star-shaped gear set, or a conical gear set with an intermediate shaft. The common transmission modes between camshaft and crankshaft include gear transmission, chain drive and toothed belt transmission. Most of thetransmission between the lower camshaft and the middle camshaft and the crankshaft are cylindrical timing gears, Generally, only 1 pair of gear is needed to be driven from the crankshaft to the camshaft. If the diameter of transmission gear is too large, 1 intermediate idler wheels can be added.To achieve smooth engagement and reduce the working noise, the timing gears mostly adopt helical gears.
Chain transmission is common between overhead camshaft and crankshaft, but its reliability and durability are inferior to gear transmission.In recent years,gear rubber belts is widely used in the high speed engine to replace the transmission chain, but chain transmission is still used in some high-power engines.
The gear rubber belts boast the advantages of small noise, reliable operation and low cost. For the DOHC, generally the exhaust camshaft is driven by a crankshaft through a timing gear rubber belts or chain , the air intake camshaft is by driven by exhaust camshaft through a metal chain ,or both the air intake camshaft and exhaust camshaft are driven by the crankshaft through gear rubber belts or chains. When installing the camshaft, be aware that attention should be payed to the timing mark on the camshaft pulley or sprocket. Some engines have no obvious timing marks, maintenance personnel can mark the exact position of the crankshaft and camshaft before removing the camshaft ,and some engines require special tools to adjust the timing.
The above is the related knowledge about the camshaft introduced by Anhui Guanshun Camshaft Manufacturing Co, Ltd. And we hope to help.