The characteristics of the camshaft

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. 
　　还有一种结构由于动力在传输过程中损耗过大且过于复杂，现在已经比较少见。这种结构通过一个偏心连杆、星形齿轮组或带中间轴的锥形齿轮组来连接顶置式凸轮轴与曲轴。凸轮轴与曲轴之间的常见传动方式包括齿轮传动、链条传动以及齿形胶带传动。下置凸轮轴和中置凸轮轴与曲轴之间的传动大多采用圆柱形正时齿轮传动，一般从曲轴到凸轮轴只需要１对齿轮传动，如果传动齿轮直径过大，可以再增加１个中间惰轮。为了啮合平稳并降低工作噪声，正时齿轮大多采用斜齿轮。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.