1 variable valve timing and lift electronic control system VTEC
VTEC system stands for a variable valve timing and lift electronic control system, proprietary technology Honda, as the engine it changes in the operating parameters of speed, load, temperature and the like, while appropriately adjusting the valve timing and valve lift of the engine at high and low speed can reach the maximum efficiency. In VTEC system, which has the intake camshaft, respectively, three cam surfaces, respectively, a top shaken three rocker arm shaft, when the engine is in a low speed or low load, no connection between the three rocker arms, left and right rocker arms are movable top two intake valves, so that the two different timing and lift, to form a squish effect. At this time, the intermediate speed rocker arm does not move the valve top, but do not valid in the rocker arm shaft motion. When the rotational speed during rising, each sensor of the monitored engine load, speed, vehicle speed and the water temperature and other parameters to the computer, the computer analysis and processing of information. When the high-speed mode to achieve the desired conversion, the computer issues a signal to open the VTEC solenoid valve, the pressure oil into the top of a piston movable within the rocker shaft, so that three integrally connected to the rocker arm, so that the valve works in the two high-speed mode. When the engine speed reaches a reduced need to change the valve timing again, the computer emits a signal again, VTEC solenoid valve opens at the beginning of the pressure, the pressure oil escape, the valve to return to low speed mode.
Common manufactured after the engine, the valve timing and valve lift to a fixed, unable to meet the demand of the engine intake and exhaust at different speeds. Accordingly, the conventional engine designers are considering the cam profile adopted compromise has to meet high speed also considered low. But the design of this into account to some extent limit the engine performance can not meet the current requirements of automotive engines. Accordingly, it is desirable to have such an engine which can accommodate any cam track speed, regardless of the optimum valve timing can be obtained in the fast or slow. Thus, the VVT control mechanism emerged. The variable in the gas phasePosition control mechanism is more representative of Honda’s VTEC system.
In 1989, Honda introduced a self-developed ldquo; variable valve timing and valve lift electronic control system rdquo ;, English full ldquo; Variable Valve Timing and Valve Lift Electronic Control Systemrdquo ;, abbreviation is ldquo; VTECrdquo ;, is the world’s first open valve can simultaneously control two different situations valve closing timing and lift of the control system and the like. Honda’s VTEC engine has been enjoyed ldquo; rdquo synonymous with variable valve engine; said, it’s not just super-horsepower output, emissions and environmental protection, low fuel consumption characteristics when it has a low speed, and this is completely different characteristics It appears above the same engine, because it has a variety of different angles of the cam on a camshaft.
and, like many ordinary engine, VTEC engine has four valves per cylinder (2 intake row 2), camshaft and rocker arms, but the number is different from the ordinary engine and the control method of the cam and the rocker arm. In low speed with a small angle of the cam, the low speed at two different valve lift and valve timing, a valve lift at this time is small, almost does not participate in the intake process, the intake-valve passage essentially corresponds to two engine, since the intake air flow direction but does not pass through the center of the cylinder, it can produce a strong intake swirl, for a low speed, especially under cold conditions conducive to improve the uniformity of air-fuel mixture, the combustion rate is increased, reducing the chill wall Effects of the clearance and the combustion more fully, thereby improving the economy and significantly reduce the HC, CO emissions; and at high speed, by VTEC solenoid valve to control the hydraulic oil, so that the two intake rocker arm integrally connected by the longest on-time, the maximum lift of the cam to drive the intake valve, the intake valve case two synchronously follow the contours of the large cam. Compared with low-speed operation, greatly increases the duration of the intake flow area and the opening, thereby improving the power performance at high engine speeds. The two output curves of completely different performance, Honda engineers so that they achieve the same engine, and vividly called ldquo; usually soft driving rdquo; and ldquo; intense driving wartime rdquo ;.
However VTEC system for changing the valve timing is still stage, which changes the valve timing that is just jumping at a certain speed, rather than over a period of continuously variable speed range. In order to improve the performance of the system VTEC, Honda continued to innovate, launch i-VTEC system.
Briefly, i-VTEC VTEC system is based on the system, adds a called VTC (Variable timing controlldquo; variable timing control rdquo;) means a mdash; mdash; group into a a variable camshaft timing control means, i.e., i-VTEC = VTEC + VTC. At this time, the exhaust valve timing and opening time of the overlap is variable, controlled by the VTC, VTC mechanism is introduced in the engine rotational speed can have a wide range of suitable valve timing, which largely increase the performance of the engine.
A typical system consists of VTC actuator VTC, VTC hydraulic control valve, consisting of various sensors and the ECU. VTC actuator, hydraulic control valve VTC may generate an operation signal in accordance with the ECU, the intake camshaft phase changes continuously. VTC make more precise the valve overlap period to ensure that intake and exhaust valves of the best overlap time, the engine power can be increased by 20 percentage. Import
VTC mechanism, so that the valve timing of the valve can be ldquo; intelligently rdquo; adapt to changes in engine load. VTC with the VTEC system during engine operation role mainly used in three ways.
1, the optimum idle / lean combustion region:
In this region, the VTC system is deactivated, the minimum angle at this time the valve overlap, due to the action of VTEC, a strong vortex, thereby the engine idle speed is stable.
2, optimum fuel consumption, exhaust control region
In this region, VTEC play a role in generating a strong vortex, so that more uniform mixing of the combustible mixture. VTC act simultaneously increase of the valve overlap angle, the partial exhaust gas re-sucked into the cylinder, the EGR played a role, in order to achieve optimum fuel consumption and exhaust control.
3, optimum torque control region
In this region, by controlling the VTC, the most appropriate valve overlap angle, while cooperating VTEC system such that the output torque of the engine to maximize.
In addition, i-VTEC engine with an intake manifold front, of an exhaust manifold disposed in the rear. Shortens the length of the exhaust manifold, i.e. shorten the distance between the three-way catalyst of the catalytic converter into the proper operating temperature faster, can effectively control emissions. Since the i-VTEC engine is started after the system enters the state, regardless of the low-speed or high-speed VTC are at work, to eliminate it? The original VTEC system deficiencies exist.
In summary, the i-VTEC system introduced VTC mechanism, so that the valve timing of the engine can be matched with the load of the engine flexibly, at any operating condition of the engine, you can find the most excellent valve timing, optimum valve overlap angle, implementation, low-speed low fuel consumption, low emission, high-speed high-power, high torque, which is controlled so as according to the requirements of the human brain, thus graphically described it is ldquo; intelligent rdquo;. VTEC