The camshaft is a part of the piston engine. Its role is to control the valve opening and closing action. Although the speed of the camshaft is half of the crankshaft in the four-stroke engine (the camshaft is the same as the crankshaft in the two-stroke engine), it is usually very high in speed and requires a lot of torque, Camshaft in the strength and support requirements are high, the material is generally special cast iron, and occasionally with forgings. As the valve movement law relates to the engine's power and operation characteristics, so the camshaft design in the engine design process occupies a very important position.
The main body of the camshaft is a cylindrical rod with the same length as the cylinder block. There are a number of cams that are used to drive the valve. One end of the camshaft is the bearing support point and the other end is connected to the drive wheel.
The side of the cam is egg-shaped. The purpose of its design is to ensure that the cylinder fully into the air and exhaust, specifically in the shortest possible time to complete the valve opening and closing action. Also taking into account the durability of the engine and the running of the ride, the valve can not open and close the operation of the acceleration and deceleration process to produce too much impact, otherwise it will cause severe valve wear, noise or other serious consequences. Therefore, the cam and the engine power, torque output and running the ride has a very direct relationship.
In general, in a straight-through engine, a cam corresponds to a valve, a V-type engine or a horizontal opposing engine is a cam that shares every two valves. While the rotor engine and the valveless valve engine due to its special structure, do not need cam.
In order to improve the power of the engine, some modified shop on the engine camshaft was modified, which facelift high-angle camshaft (Hi-CAM) is a common modification method. This modification is not complicated, but because some of the modified personnel on the camshaft cam on the working angle and working principle of understanding, making the modified effect is not obvious or even lead to deterioration of the engine performance.
The camshaft is one of the key parts of the engine. The hardness and white layer depth of the camshaft peach tip are key technical indicators that determine the service life of the camshaft and the engine efficiency. In the premise of ensuring that the cam has a sufficiently high hardness and a relatively deep white layer, it should also be considered that the journal does not exhibit higher carbides and has good cutting performance.
The camshaft is driven by the crankshaft, and its transmission mechanism is gear type, chain type and toothed belt type. The gear transmission is used for the transmission of the lower and center camshafts. Gasoline engines generally only use a pair of timing gears, that is, crankshaft timing gears and camshaft timing gears. Diesel engines need to drive diesel fuel injectors at the same time, so add an intermediate gear. In order to ensure smooth gear meshing, low noise, low wear, timing gears are cylindrical helical gears and made of different materials. Crankshaft timing gears are made of medium carbon steel, and camshaft timing gears are made of cast iron or cloth. In order to ensure the correct timing of the valve and fuel injection timing, in the transmission gear engraved with a timing mark, the assembly must be positive mark. The chain drive mechanism is used for the transmission of the center and upper camshafts, especially the high speed gasoline engine of the upper camshaft. The chain is generally a roller chain, work should maintain a certain degree of tension, not to produce vibration and noise. To this end, the chain drive mechanism is provided with a guide plate and a tensioner in the chain of the loosening device.