Camshaft The camshaft is a component in a piston engine […]
The camshaft is a component in a piston engine. Its function is to control the opening and closing of the valve. Although the speed of the camshaft in a four-stroke engine is half that of the crankshaft (in a two-stroke engine, the speed of the camshaft is the same as the crankshaft), but usually its speed is still very high and it needs to withstand a lot of torque. Camshafts have high requirements in terms of strength and support, and their materials are generally high-quality alloy steel or alloy steel. Since the valve motion law is related to the power and operating characteristics of an engine, the camshaft design occupies a very important position in the engine design process.
Camshaft working conditions and materials
The cam bearing is subjected to periodic shock loads. The contact stress between the cam and the tappet is very high, and the relative sliding speed is also very high, so the wear of the cam working surface is more serious. In response to this situation, the camshaft journal and cam working surface should have high dimensional accuracy, small surface roughness and sufficient rigidity, as well as high wear resistance and good lubrication.
Camshafts are usually forged from high-quality carbon steel or alloy steel, and can also be cast with alloy cast iron or ductile iron. The journal and cam working surface are polished after heat treatment.
The main body of the camshaft is a cylindrical rod with approximately the same length as the cylinder group. There are several cams on it, which are used to drive the valve. The camshaft is supported in the camshaft bearing hole through the camshaft journal, so the number of camshaft journals is an important factor affecting the stiffness of the camshaft support. If the camshaft has insufficient rigidity, it will bend and deform during operation, which will affect the timing of the gas distribution.
The side of the cam is egg-shaped. The purpose of its design is to ensure adequate intake and exhaust of the cylinder. In addition, considering the durability of the engine and the smoothness of operation, the valve should not have too much impact due to the acceleration and deceleration process in the opening and closing action, otherwise it will cause severe valve wear, increased noise or other serious consequences. Therefore, the cam has a direct relationship with the engine's power, torque output, and smoothness of operation.