Most TOYOTA cars produced in recent years have assembled an engine labeled with "VVT-i". After commercial publicity, many people have known the new term "VVT-i", but the specific content of it is rarely known. VVT is the English abbreviation, the full name is "Variable Valve Timing", the Chinese meaning is "variable valve timing", because of the use of electronic control unit (ECU) control, so TOYOTA has a good Chinese name called "intelligent variable valve timing system". The system mainly controls the intake camshaft, and has a small tail "I", which is the code of English "Intake". These are the literal meanings of "VVT-i".

VVT-i is a device to control the intake camshaft valve timing. It is optimized by adjusting the timing of the camshaft angle distribution, thus improving the engine's power, fuel economy and exhaust emission in all the rotational speed ranges.

The VVT-i system consists of sensors, ECU and camshaft hydraulic control valves, controllers and so on. The optimal valve timing parameters are stored in ECU. The feedback information of the crankshaft position sensor, the air pressure sensor, the throttle position sensor, the water temperature sensor and the camshaft position sensor is gathered to ECU and is compared with the predetermined parameter values, and the correction parameters are calculated and the instructions are sent to the control camshaft. In the hydraulic control valve, the control valve controls the position of the oil slot valve according to the ECU instruction, that is to change the hydraulic flow, and transfer the signal instructions in advance, lag, and keep to the different oil channels of the VVT-i controller.

The VVT-i system is divided into two different parts of the controller, one is installed on the exhaust camshaft, it is called the blade VVT-i, and the TOYOTA PREVIA is installed. The other is installed on the intake camshaft, known as spiral groove VVT-i, TOYOTA Lexus 400, 430 and other senior cars to install this section. The two structures are somewhat different, but the effect is the same.

The vane VVT-i controller consists of the tube shell driving the intake camshaft and the impeller coupled with the exhaust camshaft. The oil pressure from the advance or lag side oil channel is transferred to the exhaust camshaft, resulting in the rotation of the VVT-i controller shell to drive the intake camshaft, and the intake timing is continuously changed. When the oil pressure is applied to the early side oil chamber, the intake camshaft is rotated in the early direction; when the oil pressure is applied to the housing of the lag side oil chamber, the intake camshaft is rotated along the lag direction; when the engine stops, the camshaft hydraulic control valve is in the largest lagging state.

A spiral groove VVT-i controller includes a gear driven by a timing belt, an inner gear with a rigid connection with the intake camshaft, and a movable piston between the inner and outer gears. The piston surface has a spiral spline. The piston moves along the axis and changes the phase of the inner and outer gears, thus producing the valve timing phase. Change continuously. When the oil pressure is applied to the left side of the piston, the piston is moved to the right. The intake camshaft will advance to a certain angle relative to the camshaft timing pulley due to the function of the spiral spline on the piston. When the oil pressure is applied to the stone side of the piston, forcing the piston to move left, the intake camshaft will be delayed at some angle. When the ideal timing of valve timing is achieved, the camshaft timing hydraulic control valve will turn off the oil path to balance the pressure on both sides of the piston, and the piston will stop moving.

Now, advanced engines have "engine control module" (ECM), ignition, fuel injection, emission control, fault detection and so on. The ECM of the TOYOTA VVT-i engine automatically searches for an optimal valve timing that corresponds to the engine speed, intake, throttle position and cooling water temperature in various driving conditions, and controls the camshaft timing hydraulic control valve, and perceives the actual valve timing through the signals of the various sensors, and then the feedback control is carried out, and then the feedback control is carried out. The system error can be compensated to achieve the optimal valve timing position, so that the power and performance of the vehicle can be effectively improved, and the fuel consumption and exhaust emission can be minimized.

VVT is the English abbreviation, the full name is "Variable Valve Timing", the Chinese meaning is "variable valve timing", because of the use of electronic control unit (ECU) control, so TOYOTA has a good Chinese name called "intelligent variable valve timing system". The system mainly controls the intake camshaft, and has a small tail "I", which is the code of English "Intake". These are the literal meanings of the "VVT-I".