automotive engine valve timing when the mechanisms and techniques, also called a continuously variable valve timing system, today’s high performance engine with the general system. The system is equipped with control and execution by the system, the phase of the engine cam or valve lift is adjusted so as to optimize the process object of the engine valve.
1 variable valve noun
automotive engine valve timing when the mechanisms and techniques, also called continuously variable valve timing system, generally equipped with high-performance engines of today the system. The system is equipped with control and execution by the system, the phase of the engine cam or valve lift is adjusted so as to optimize the process object of the engine valve.
variable valve timing technology has become almost standard in today’s engines, in order to further tap the potential of conventional internal combustion engines, engineers and on this basis, developed a variable valve lift technology, when an effective combination of the two, providing higher compared with the engine intake and exhaust efficiency in various operating conditions and speed. Enhance the power, but also reduces fuel consumption levels.
2. The principle variable valve
because of high speed and low speed, the impact angle of the valve timing of the engine power and economy will be apparent, can take advantage of high speed intake inertia and improve the scavenging efficiency of the intake air amount, so that the valve opening late and closing early, low speed and vice versa, the engine now has mostly the art.
3. The origin of the variable valve
by a piston four-stroke engine, the intake, compression, power, exhaust four stroke is completed, we are concerned with the degree of valve opening the question of engine intake. The basic principle of the cylinder intake air is “negative”, i.e. the gas pressure difference between inside and outside the cylinder. When the engine at low speed, the degree of opening of the valve must not be too large, so easily lead to internal and external pressure equalization cylinder, negative pressure decreases, the intake is not sufficient for the valve work is concerned, this “small degree on” needs a short trip be controlled waySystem; high speed on the contrary, the speed at every turn 5000rpm, if still shy refused to open the valve, engine intake inevitable blocked, so we need a long stroke of valve lift. Often, engineers have to take into account not only the engine torque characteristics in the low-speed region, want to squeeze the power characteristics of the high-speed zone, but to take a “compromise” the idea, did not end the high-speed engine power, the lack of low-speed torque.
Therefore, in this case, it is a need for a device for adjusting the valve lift, that is we say “variable valve timing.” The technology can guarantee low speed high torque, high speed and high power can be obtained, for engines, it is a great breakthrough.
1980s, many companies began to put research at the positive variable valve timing, for the first time in 1989, Honda issued a “variable valve valve timing and valve lift electronic control system,” the English name “Variable Valve Timing and Valve Life Electronic Control System, which is our common VTEC. Since then, various companies continue to develop the technology, and today has been very mature, Toyota also developed VVT-i, Porsche developed Variocam, almost modern developed DVVT …… each company has its own variable valve timing technology. Although a series of variable valve timing technology trade names vary, but its design is extremely similar.
4. the principles and valve timing mechanism
effect
as we all know, the engine valve timing mechanism responsible for providing the combustion gas to the cylinders of the workMust be fresh air and exhaust gas discharged after combustion, this operation can be seen as a human inhalation and exhalation processes. From the working principle, the main function of the valve timing mechanism according to a certain timing to open and close each cylinder intake and exhaust valves, in order to achieve the overall ventilation of the engine cylinder replenishment.
then the valve principle and function and how should understand? We can be likened valve engine is a door, open the door of the size and the length of time to determine the flow of people in and out. The larger door opening angle, the longer the time of opening, the greater the flow of people in and out, and vice versa. On the engine for the same reason, the concept arises valve lift and timing of. As if the valve lift doors open angle valve timing as if the door open time. Three-dimensional thinking to look at the issue perspective, the perspective of time is added to the size of a space, it also determines the unit time of import and displacement.
5. Advantage variable valve timing and lift technology
Typically the engine valve driven by the camshaft, the engine is not normal for a variable valve timing technologies, into, they exhaust opening and closing time is fixed, but this fixed valve timing Shique difficult to take into account the need of the engine at different speeds and operating conditions. He said before the engine intake, exhaust process of the human body is like breathing, but fixed “breathing” rhythm was hampered enhance engine efficiency.
If you participated in a long distance race, will be able to deeply understand the importance of breathing rhythm grasp of the physical play – too hasty or deliberate breath may increase the fatigue, the desire to reduce the run. therefore weWhen long-distance race often need to continue to follow the pace of the run to adjust the respiratory rate, are available to provide sufficient oxygen for the body. For automobile engine, the same principle applies. Variable valve timing and lift technology is to allow the freedom to adjust the engine to “breathe” in a variety of load and speed, so as to enhance dynamic performance, improve the combustion efficiency.