The function of the valve is specially responsible for inputting air into the engine and discharging exhaust gas after combustion. From the engine structure, it can be divided into intake valve and exhaust valve. The function of the intake 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.

The valve consists of a valve head and a stem. The temperature of the valve head is very high, and it also bears the pressure of gas, the force of the valve spring and the inertia force of the transmission assembly. Its lubrication and cooling conditions are poor, which requires the valve to have certain strength, stiffness, heat resistance and wear resistance.

Generally, alloy steel is used for intake valves and heat-resistant alloy is used for exhaust valves. Sometimes in order to save heat-resistant alloy, the exhaust valve head is made of heat-resistant alloy and the valve stem is made of chromium steel, and then the two are welded. The shape of the valve head includes flat top, spherical top and trumpet top. Generally, flat roof is adopted.

The invention has the advantages of simple structure, convenient manufacture, small heat absorption area and light weight, and can be used for intake valves and exhaust valves. Spherical top valve is suitable for exhaust valve, which has high strength, low exhaust resistance and good exhaust elimination effect, but it has large heating area, large mass, large inertia and complicated processing. Horn type has a certain streamline, which can reduce intake resistance, but its head has a large heating area and is only suitable for intake valve.

condition

In order to improve the efficiency of intake and exhaust, multi-valve technology is often used. It is common that each cylinder is equipped with four valves (there are also three or five valves in a single cylinder, and the principle is the same, such as the engine of Audi A6). There are * * valves 16 in the four cylinders, and the "16V" we often see in the automobile data is * * 65438+.

This multi-valve structure is easy to form a compact combustion chamber, and the fuel injector is arranged in the center, so that the fuel-air mixture burns faster and more evenly, and the weight and opening of each valve can be reduced appropriately, so that the valves can be opened or closed faster.