The main body of the camshaft is a cylindrical rod of equal length to the cylinder bank. On the rod body, a number of cams are installed, each CAM has its own function, corresponding to the control of one or a group of valves. Take the in-line engine as an example, usually one CAM matches one valve; In V-type engines or horizontally opposed engines, one CAM is generally shared for each of the two valves. The side of the CAM has a unique egg shape, which is of great significance. On the one hand, it ensures that the opening and closing actions of the valve are completed in the shortest possible time to meet the needs of the engine for efficient air exchange; On the other hand, the durability and running smoothness of the engine are fully considered to avoid excessive impact caused by acceleration and deceleration of the valve during opening and closing, and to prevent excessive wear and noise of the valve. In addition, one end of the camshaft is used as the bearing support point to ensure smooth operation; The other end is connected to the drive wheel to receive power from the crankshaft and achieve power transmission.
In view of the camshaft is subjected to periodic impact load, the contact stress between CAM and tappt is large and the relative sliding speed is high, which is easy to cause the working surface of CAM wear, so the material requirements are very strict. Commonly used materials are special cast iron, high-quality carbon steel, alloy steel, alloy cast iron and ductile cast iron, etc. Special cast iron with good wear resistance and casting properties, has become a more commonly used material; High quality carbon steel and alloy steel after forging, with high strength and toughness, can adapt to high load work; Alloy cast iron and ductile cast iron in the casting process, can meet the needs of complex structures, and the cost is relatively low. In order to further improve the wear and fatigue resistance of the camshaft, the journal and CAM working surface are often heat treated, such as quenching, tempering, etc., followed by polishing treatment to reduce surface roughness and reduce wear.
