The principle of variable valve timing technology, the principle of operation of variable timing val

The valve timing system of the traditional engine is a kind of mechanical system in which the valve phase is opened and closed, and the valve opening and closing is unchanged, and the valve system is difficult to meet the needs of the engine for gas distribution under a variety of working conditions, and can not meet the requirements of the engine to output strong power under various speed conditions. The variable valve timing system is an electronic control system that changes the opening time or opening size of the valve, and enhances the balance of the vehicle's torque output, improves the engine power and reduces the vehicle's fuel consumption by matching a more reasonable valve opening or closing time for the vehicle at different speeds.

As can be seen from the valve phase diagram, the intake valve opens and closes late as the piston moves from top dead center to bottom dead center. When the engine has finished working and the piston is moved from bottom dead center to top dead center, the exhaust valve opens early and closes delayed.

This extended opening time of the valve inevitably leads to a moment when the intake and exhaust valves open at the same time, which is called the "overlapping phase" in the valve phase, which can cause exhaust gas backflow. This phenomenon is most noticeable at idle when the engine is only 1 000 r min or less (the "overlapping phase" time at idle is seven times longer than at medium speeds). This is easy to cause idle work is not smooth, excessive vibration, power drop and other phenomena.

In particular, in four-valve engines, due to the large value of the "curtain zone", the "overlapping phase" is more likely to cause the phenomenon of unsmooth idle operation. In order to eliminate this defect, the designers adopted a "variable" valve actuation mechanism with "change" to "change".

The variable valve actuation mechanism is to reduce the valve stroke and reduce the "curtain zone value" when the engine is working rapidly, and increase the valve stroke when the engine is working at high speed, expand the "curtain zone value", and change the time of the "overlapping phase", so that the engine can provide strong power at high speed and produce enough torque at low speed, so as to improve the working performance of the engine. The valve variable drive mechanism can change the valve phase at any time according to the operating conditions of the car, and change the valve lift and valve opening duration.

Principle: The principle of variable valve timing technology (VVT, variable valve timing) is to adjust the intake (exhaust) volume, valve opening and closing time and angle according to the operation of the engine, so that the amount of incoming air reaches the best value and improves the combustion efficiency. The advantages are fuel saving and large power-to-lift ratio; The disadvantage is that the torque in the middle section is insufficient.

Technology: VVT technology has a history of more than 30 years, and in 1980, Alfaromeo first used VVT technology; Honda, in 1989, used VVT technology with variable valve lift capability for the first time; BMW, in 2001, replaced the conventional throttle for the first time with VVT technology.

The VVT of Korean cars is based on Toyota's VVT-i and Honda's VTEC technology in Japan, but compared with Toyota's VVT-I variable timing valve technology, VVT is only variable valve technology and lacks timing technology, so the VVT engine is indeed more fuel-efficient than the general engine, but it is not as fuel-efficient as the Toyota and Honda cars of Japanese cars.

BMW has already adopted this technology in previous generations of engines, such as Honda's VTEC, i-VTEC, and current engines; Toyota's VVT-i; Nissan's CVVT; Mitsubishi's Mivec; Suzuki's VVT; modern VVT; Kia's CVVT; JAC's VVT; The Great Wall's VVT and other products are also gradually being used. In general, it is actually a technology, with a different name.

1.Variable valve timing adjusts the phase of the engine's spike cam so that the amount of air changes with the engine speed. To a certain extent, the engine can achieve maximum combustion efficiency, improve fuel economy, fully burn fuel, and reduce carbon deposits.

2.Variable valve timing, also known as VVT, has the greatest effect on reducing NOx (nitrogen oxides) and HC (hydrocarbons) emissions, thereby increasing torque at low speeds and power burnout at high speeds. The variable valve timing structure is complex and has many parts, which is mainly composed of VVT solenoid valve, engine control computer, VVT phaser, sensor and oil circuit.

When the vehicle is driving normally on the road, the engine will also work with it, especially at high speeds, when the engine needs more air. However, on the basis of high rpm, the air required for the intake valve is completely closed before entering, resulting in a decrease in performance, so the timing of the opening and closing of the valve is important. Therefore, variable valve timing is the time to do its job.

It can adjust the overlap time and timing of the engine's intake and exhaust systems to speed up fuel combustion and improve efficiency.