The valve assembly is a part of the engine valve train. It plays a very important role in engine operation. The operation of a fuel engine consists of four working processes: intake, compression, operation, and exhaust. In order for the engine to run continuously, these four working processes must be periodically cycled. The two working processes, intake and exhaust, rely on the engine's gas distribution mechanism to accurately deliver combustible mixtures (gasoline engines) or fresh air (diesel engines), as well as exhaust gases emitted after combustion, according to the working order of each cylinder. In the other two working processes, the compression and working processes must isolate the cylinder combustion chamber from the external intake and exhaust channels to prevent gas leakage and ensure the normal operation of the engine. The component responsible for the above work is the valve in the valve train. It's like a person's breathing organ, inhaling and exhaling without it.

With the development of technology, the rotational speed of automobile engines is getting higher and higher. The rotational speed of modern automotive engines can generally reach over 5500 revolutions per minute. The completion of these four work processes only takes 0.005 seconds. The traditional two valves can no longer complete the ventilation work in such a short time, which limits the improvement of engine performance. The solution to this problem is to expand the space for gas to enter and exit. In other words, swap space with. Until the 1980s, the promotion of multi valve technology made a qualitative leap in the overall quality of the engine.

A multi valve engine is a three valve type in which each cylinder has more than two valves, namely, two intake valves and one exhaust valve; A four valve type with two intake and two exhaust valves; A five valve type with three intake valves and two exhaust valves. Currently, most multi valve engines in automobiles are of the four valve type. The four cylinder engine has 16 valves, the six cylinder engine has 24 valves, and the eight cylinder engine has 32 valves. For example, the engine of Japan's Lingzhi LS400 car has 8 cylinders and 32 valves. Increase the number of valves and corresponding gas distribution mechanism devices, with a more complex structure. Generally, two top camshafts control the valves on both sides of the cylinder combustion chamber centerline. The valves are arranged in inclined positions on both sides of the center of the cylinder combustion chamber to expand the diameter of the atmospheric valve head, increase the airflow passage area, improve ventilation performance, and form a compact combustion chamber with a spark plug in the center, which is conducive to rapid combustion of the mixed gas.

The function of the valve is to draw air into the engine and mix it with fuel for combustion; The function of the exhaust valve is to exhaust the exhaust gas after combustion and dissipate heat. Excessive valve clearance: After the exhaust valve is delayed in opening, the intake and exhaust time decreases, the valve opening height decreases, and the gas distribution phase changes normally. Due to insufficient intake and dirty exhaust, the engine power decreases. In addition, it also increases the impact of valve train components, accelerating wear. Too small clearance: After the engine is operating, parts expand due to heat, pushing open the valve, resulting in lax valve closure, resulting in air leakage and reduced power, severe carbon deposition or combustion on the valve sealing surface, and even valve impact on the piston. The use of hydraulic controlled pneumatic mechanisms does not require leaving valve clearance.

Taking the gasoline engine as an example, compared to the traditional two valve engine, the former can absorb more air to mix fuel for combustion, save fuel, emit exhaust gas faster, reduce pollution, improve engine power, and reduce noise, which is in line with the development direction of optimizing the environment and saving energy. Therefore, the multi valve technology can be quickly promoted.