The inherent shortcomings of the traditional valve train. Because the movement law of the valve, including the valve lift and the continuous crank angle of the valve opening and closing, is completely determined by the contour of the valve cam, this makes the traditional valve train have its inherent shortcomings. Valve phase cannot change with operating conditions. For an engine, the cam profile has been determined, and it is impossible to change with the engine operating conditions during the working process, which results in the valve motion law and the valve valve phase determined by the valve motion law. It varies with the working conditions of the engine. This kind of valve mechanism can only satisfy the engine to obtain the maximum charging efficiency under a certain working condition, while the charging efficiency will be reduced to varying degrees in a wide range of other working conditions. It is not easy to realize the variable technology of valve valve phase. In order to make the valve valve phase change with the working conditions of the engine and try to improve the charging efficiency of the engine under various working conditions, the variable valve has been developed on the basis of the traditional valve train. The air distribution mechanism of the air phase.
There are two types of valve trains with variable valve phases currently in use. The opening and closing of the valves is still controlled by cams. The other is a valve train with variable camshaft phases. This type of valve train is controlled by a computer according to the engine’s operating conditions. If necessary, control the hydraulic system to change the relative angular position of the intake camshaft and the intake camshaft timing gear or toothed belt pulley or sprocket, thereby changing the air distribution phase. Since the cam profile has not changed, although the opening and closing moments of the intake valve have changed, the continuous opening angle of the intake valve has not changed, and the change in the valve stacking angle is not compatible with the changes in operating conditions. There is also no change in the phase of the exhaust valve.
The other is a valve train with variable intake duration. It is equipped with two sets of intake cams on the intake camshaft, namely low-lift, short-duration intake cams for medium and low speeds and high torque, and high-speed and high-power intake cams. The high-lift and long-duration intake cam used. The two sets of cams are switched by the computer controlled by the hydraulic device according to the engine working conditions. This variable system can meet the different requirements for valve timing at high and low speeds, and ensure good performance at high and low speeds, but the phase of the exhaust valve remains unchanged, and the structure is also complex, making it difficult to arrange, especially for multi-valve structures. . For automotive parts and parts machining, PTJ Shop offers the highest degree of OEM service with a basis of 10+ years experience serving the automotive industry. Our automotive precision shop and experts deliver confidence. We have perfected the art of producing large component volumes with complete JIT reliability, backed by the quality and long-term reliability our customers expect.
Link to this article：Analysis and Research on Traditional Valve Train System
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