What is a vvt engine?

VVT engine (Variable Valve Timing) is the abbreviation of variable valve timing, and it is an automobile engine with VVT system, which has the advantages of fuel saving and high power lift ratio. The disadvantage is the lack of speed and torque in the middle section. The following is what my vvt engine is. Welcome to reading.

VVT is the abbreviation of VariableValveTiming, which means variable timing valve system. This technology itself is not magical, but it has a certain effect of turning decay into magic. Its characteristics are that it can ensure stable combustion, reduce fuel consumption, effectively improve the emission of hydrocarbons and nitrogen oxides, and at the same time, it can expand volumetric efficiency and improve combustion performance. Of course, the principle of VVT technology is actually very simple: because the power required by the engine is different at different times, VVT technology can adjust the air intake by adjusting the valve opening, so that the engine can have an ideal working state at different speeds: delaying the opening time of the intake valve, reducing the valve overlap angle, stabilizing the idle combustion state, reducing the fuel consumption and pollution emissions under medium working conditions (medium speed and constant speed driving), and improving the high-speed working efficiency of the engine; The opening time of intake valve is advanced, and the valve overlap angle is increased, so as to obtain greater torque under low speed and heavy load conditions (starting, accelerating and climbing).

VVT engine, CVVT engine and VTEC engine are actually gasoline engines of the same generation technology. Both refer to continuously variable valve timing technology and variable intake and exhaust manifold length technology. According to the different working conditions of the engine, the power performance and fuel economy of the engine can be improved by adjusting the valve closing timing and the length of the intake and exhaust manifold.

The advantages are:

1, low fuel consumption

2. Strong motivation

3. Environmental protection

Disadvantages are:

1, the engine is too dependent on electronic technology.

2. The requirements for gasoline labels have been improved.

Explanation 3. The technology adopted by VVT engine, that is, continuously variable valve timing technology, can continuously adjust the valve opening and closing time and air intake of the engine, thus improving engine power, optimizing torque curve, improving product power and reducing fuel consumption. VVT technology is the trend of automobile power development.

principle

Vvt engine, variable valve timing system (VVT), which adjusts the phase of the engine cam through the equipped control and execution system, so that the time of valve opening and closing changes with the change of engine speed, thus improving the charging efficiency and increasing the engine power. VVT technology has a history of more than 30 years. 1980, AlfaRomeo used VVT technology for the first time. Honda, 1988, used VVT technology with variable valve lift for the first time; Bmw, at 200 1, used VVT technology to replace the traditional throttle for the first time. Its principle is to adjust the intake (exhaust) amount, valve opening and closing time and angle according to the engine operation, so that the intake amount can reach the optimal value and the combustion efficiency can be improved. Its advantages are fuel saving and high power ratio; The disadvantage is the lack of speed and torque in the middle section.

origin

Vvt engine schematic diagram VVT means "variable valve timing" in Chinese. Because it is controlled by electronic control unit (ECU), Toyota has a nice Chinese name "Intelligent Variable Valve Timing System". The system mainly controls the intake camshaft, and has a small tail "I", which is the code name of English "intellingence". These are the literal meanings of "vvt-I". VVT-I system is the abbreviation of Toyota Intelligent Variable Valve Timing System, which has been widely installed in the latest Toyota engine. Toyota's VVT-I system can continuously adjust the valve timing, but it cannot adjust the valve lift. Its working principle is that when the engine changes from low speed to high speed, the electronic computer automatically presses the engine oil to the small turbine in the driving gear of the intake camshaft, so that the small turbine rotates at a certain angle relative to the gear box under the pressure, and the camshaft rotates forward or backward within 60 degrees, thus changing the opening time of the intake valve and achieving the purpose of continuously adjusting the valve timing.

technology

1, VVT engine The VVT of Korean cars is based on the VVT-I technology of Toyota in Japan and the VTEC technology of Honda. However, compared with Toyota's VVT-I variable timing valve technology, VVT is only a variable valve technology, lacking timing technology, so VVT engine is indeed more fuel-efficient than ordinary engines, but not as fuel-efficient as Toyota and Honda cars of Japanese cars. BMW has adopted this technology in the previous generation engines, such as Honda's VTEC, i-VTEC,; Toyota's vvt-I; Nissan's CVVT；; ; Mivik; Mitsubishi; Suzuki's VVT；; ; Modern VVT；; ; Kia's CVVT；; ; VVT； Jianghuai; The VVT of the Great Wall has gradually begun to be used. Generally speaking, it is actually a technology with different names.

2.VVT-I is a device to control the valve timing of the intake camshaft. By adjusting the valve timing of camshaft angle, the power and fuel economy of the engine in all speed ranges are improved and the exhaust emission is reduced. VVT-I system consists of sensor, ECU, camshaft hydraulic control valve and controller. The ECU stores the optimal valve timing parameter values, and feedback information such as crankshaft position sensor, intake manifold pressure sensor, throttle position sensor, water temperature sensor and camshaft position sensor is collected in the ECU and compared with the predetermined parameter values to calculate the correction parameters and send instructions to the hydraulic control valve to control the camshaft timing. The control valve controls the position of the oil pan valve according to the instruction of ECU, that is, changes the hydraulic flow, and selectively sends signal instructions such as advance, delay and invariability to different oil circuits of VVT-I controller.

use

According to the installation position of the controller, VVT-I system can be divided into two types. One type is installed on the exhaust camshaft, which is called vane VVT-I, and Toyota Previa installed this type. The other is installed on the intake camshaft, called spiral groove VVT-I, and installed on Toyota Lexus 400, 430 and other advanced cars. Their structures are somewhat different, but their functions are the same.

Schematic diagram of vvt engine The vane VVT-I controller is composed of a housing driving the intake camshaft and an impeller coupled with the intake camshaft. The oil pressure from the leading or lagging oil passage is transmitted to the exhaust camshaft, which makes the shell of VVT-I controller rotate, drives the intake camshaft and continuously changes the intake timing. When the oil pressure is applied to the advance side oil chamber rotating housing, the intake camshaft rotates in the advance direction; When the oil pressure acts on the rotating housing of the oil cavity on the lagging side, the intake camshaft rotates in the lagging direction; When the engine is stopped, the camshaft hydraulic control valve is in the maximum lag state.

The spiral groove VVT-I controller includes a gear driven by a timing belt, an internal gear rigidly connected with the intake camshaft, and a movable piston located between the internal gear and the external gear. There are spiral splines on the surface of the piston, and the piston moves along the axial direction, which will change the phase of the internal gear and the external gear, thus causing the continuous change of the valve distribution phase. When the oil pressure is applied to the left side of the piston, forcing the piston to move to the right, the intake camshaft will advance by a certain angle relative to the camshaft timing pulley due to the helical spline on the piston. When the oil pressure is applied to the stone side of the piston, forcing the piston to move to the left, it will delay the intake camshaft by a certain angle. When the ideal valve timing is obtained, the camshaft timing hydraulic control valve will close the oil passage to balance the pressure on both sides of the piston and the piston will stop moving.

Advanced engines have "Engine Control Module" (ECM), which is responsible for ignition, fuel injection, emission control, fault detection and so on. The ECM of Toyota VVT-I engine automatically searches for the optimal valve timing corresponding to engine speed, air intake, throttle position and cooling water temperature under various driving conditions, and controls the camshaft timing hydraulic control valve. The actual valve timing is sensed through the signals of various sensors, and then feedback control is carried out to compensate the system error and reach the optimal valve timing position, thus effectively improving the power and performance of the automobile and minimizing the fuel consumption and exhaust emissions.

applied range

VVT technology, which is very helpful for fuel saving, has been widely used, such as Zhengzhou Nissan Junfeng.

Junfeng is equipped with the latest Dongfeng Chen Xin DFXC 13 series engine, and adopts double overhead camshaft, DIS direct ignition system, 16 valve and air intake VVT technology.

Junfeng's engine has a maximum power of 65KW and a maximum torque of 120 Nm.

The power is higher than the same level, and the power is strong under full load. At the same time, the engine adopts air intake VVT technology to make fuel burn more fully, thus reducing fuel consumption.

In addition, with the special engine oil, gearbox oil and rear axle oil developed by Castrol for Junfeng, according to the actual measurement in Germany, the fuel economy can reach 3.3%, especially in today's soaring oil prices.