1886 65438+1On October 29th, German Carl Benz installed his own four-stroke single-cylinder fuel engine on a three-wheeled vehicle and obtained the patent right. The world really had a car from this day on. It can be said that the engine created the car. The basic structure of the engine consists of 1 cylinder, piston 2, connecting rod 3 and crankshaft 4. Each cylinder has at least two valves, an intake valve (blue) and an exhaust valve (orange).
The valve device is an integral part of the engine valve train and plays a very important role in the engine work. The operation of a fuel engine consists of four working processes: intake, compression, work and exhaust. In order to make the engine run continuously, it is necessary to make these four working processes work repeatedly and periodically.
Two of the working processes, intake and exhaust, need to rely on the valve train of the engine to accurately deliver combustible mixture (gasoline engine) or fresh air (diesel engine) according to the working sequence of each cylinder, and discharge the burnt exhaust gas. The other two working processes, compression and work, 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 part responsible for the above work is the valve in the valve train. It is like a human respiratory organ, inhaling and exhaling, and it is indispensable.
With the development of science and technology, the speed of automobile engine is getting higher and higher. The speed of modern automobile engine can generally reach more than 5500 revolutions per minute, and it only takes 0.005 seconds to complete four working processes. The traditional two valves are no longer competent to complete the ventilation work in such a short time, which limits the improvement of engine performance. The only way to solve this problem is to expand the space for gas to enter and exit. In other words, space brings time. Multi-valve technology is the best way to solve this problem. It was not until the popularity of multi-valve technology in the 1980s that the overall quality of the engine made a qualitative leap.
Multi-valve engine refers to a three-valve type with more than two valves per cylinder, namely, two intake valves and one exhaust valve; Four-valve type, with two intake valves and two exhaust valves; Five-valve type with three intake valves and two exhaust valves. At present, the multi-valve engines in automobiles are mostly four-valve engines. Four-cylinder engine has 16 valves, six-cylinder engine has 24 valves, and eight-cylinder engine has 32 valves. For example, the engine of the Lexus LS400 sedan in Japan is 8 cylinders and 32 valves. When the number of valves increases, corresponding valve mechanism devices need to be added, which has a complex structure. Generally, two overhead camshafts are used to control the valves arranged on both sides of the center line of the cylinder combustion chamber. The valves are arranged at the inclined positions on both sides of the center of the cylinder combustion chamber, in order to enlarge the diameter of the valve head as much as possible, increase the air flow area, improve the ventilation performance, and form a compact combustion chamber with a spark plug in the center, which is beneficial to the rapid combustion of the mixed gas.
Someone asked, since the valves are good, why can't you see an engine with more than six valves in one cylinder? Thermodynamics has a concept called "curtain area", which refers to the circle of the valve multiplied by the lift of the valve, that is, the space where the valve opens. The larger the "curtain area", the larger the opening space of the valve and the larger the air intake. Take the engine of Audi 100 car as an example, its four-valve "curtain area" value is half that of two valves, and the intake state and exhaust state are both 70% larger. Of course, everything has its scope of application, which does not mean that the more valves, the greater the value of "curtain wall area". According to experts' calculation, when the number of valves per cylinder increases to 6, the value of "curtain area" will decrease. The more valves, the more complicated the mechanism and the greater the cost. Therefore, at present, the number of valves in each cylinder of automobile multi-valve fuel engine is three to five, of which four valves are the most common.
Take a gasoline engine as an example. Compared with the traditional two-valve engine, the multi-valve engine can inhale more air to burn mixed fuel, save fuel, discharge exhaust gas faster and cause less pollution. It can improve engine power and reduce noise, which is in line with the development direction of optimizing environment and saving energy. Therefore, multi-valve technology can be rapidly popularized.
When the multi-valve fuel engine began to rise, some people thought that it had a technical defect, that is, it could not run smoothly at low speed. The famous German Porsche Automobile Company held this view. With the continuous progress of technology, this technical defect of multi-valve gas engine has been gradually overcome. In recent years, Porsche 944S2 has been equipped with a four-cylinder four-valve engine. At present, almost all mid-to high-end cars in the world are equipped with multi-valve fuel engines. report
What is the maximum number of valves per cylinder of the engine?
Multi-valve engine refers to a three-valve type with more than two valves per cylinder, that is, two intake valves and one exhaust valve; Four-valve type, with two intake valves and two exhaust valves; Five-valve type with three intake valves and two exhaust valves.
Thermodynamics has a concept called "curtain area", which refers to the circle of the valve multiplied by the lift of the valve, that is, the space where the valve opens. The larger the "curtain area", the larger the opening space of the valve and the larger the air intake. Of course, everything has its scope of application, which does not mean that the more valves, the greater the value of "curtain wall area". According to experts' calculation, when the number of valves per cylinder increases to 6, the value of "curtain area" will decrease. The more valves, the more complicated the mechanism and the greater the cost. Therefore, at present, the number of valves in each cylinder of automobile multi-valve fuel engine is three to five, of which four valves are the most common.